Class Iiiii_ql 
 
 Book ^4— 
 
 CoipghtN" 
 
 COPYRIGHT DEPOSIT 
 
CENTRAL STATION 
 EXPERIENCES 
 
 A series of narratives on the trials 
 
 and tribulations of a steam 
 
 eng^ineer while learning; 
 
 to run an electric 
 
 station 
 
 FROM 
 
 I e c ) o 3 
 
 ■) 1 } J , 3 , 
 
 NEW YORK 
 
 THE POWER PUBLISHING CO. 
 
 WORLD BUILDING 
 I90I 
 
^/(f 
 
 THE LI9«ARV OF 
 
 CONGRESS, 
 Two Copies Receivep 
 
 WAY. 31 1901 
 
 CoPYRtCrtT ENTRY 
 
 CLASS O/XXc. N». 
 I COPY B. 
 
 Copyright, J 90 1, by 
 The Power Publishing Co, 
 
 Tfif// 
 
 « « «< 
 
 c c 
 
 
CONTENTS, 
 
 A Defective Arc Lamp i 
 
 Excessive Drop in Three- Wire Circuits 9 
 
 Careless Paralleling of Dynamos 15 
 
 A "Dead" Dynamo and Hot Field Coils 23 
 
 A "Breaking" Arc Circuit — Simple Ground Detector 31 
 
 Another Case of "Dead" Dynamo — Low Voltage 38 
 
 Careless Motormen — An Equalizer Trouble 42 
 
 A Sparking Motor — Motor Wiring 47 
 
 Some Railway Kinks 53 
 
 Reading a Recording Wattmeter 59 
 
 Braking a Car with Its Motor (i^ 
 
 Enlarging a Running Station — The Motor Balancer 74 
 
 A Simple Trouble, with Annoying Results 81 
 
 Transformers on Three-Wire Secondaries 87 
 
 A Long Circuit from Ordinary Generators — Two-Phase Motors on 
 
 Single-Phase Generators 93 
 
 Increasing the Output of an Alternator — Wiping Out Inductive 
 
 Drop 100 
 
A DEFECTIVE ARC LAMP. 
 
 The water-works plant of the town of Millville had been aug- 
 mented by an electric lighting plant, comprising a 50-light Brush 
 arc dynamo and two 500-light incandescent machines, with the 
 necessary circuits and appurtenances. The engineer, who was a 
 bright fellow, and had studied as much as his limited opportun- 
 ities would allow, was without practical experience in the opera- 
 tion of electrical machinery, and was correspondingly nervous 
 over his new responsibilities. 
 
 "You see," he confided to Jones, who installed the. plant, ''I 
 never actually run one of these blamed things, though I've been 
 over to the Watertown station a good deal, and watched 'em 
 running." i 
 
 "Don't you worry a mite," said Jones; "I'll be through here 
 every few weeks, and I'll always stop off to see how you're get- 
 ting on," which he did faithfully. 
 
 The plant was duly started up by Jones, who remained a week 
 to get the engineer fairly started, and things went swimmingly 
 until one night when the "trimmer," who looked out for the arc 
 lamp circuits, came rushing in and exclaimed: 
 
 "The lamps are all upside down; turn her around quick!" 
 
 The engineer stared. 
 
 "Upside down? I haven't touched 'em. Turn who around — 
 what—" 
 
 "They're burning backwards, man; can't you see?" 
 
 "No, I can't see. What are you talking about?" 
 
 The trimmer had had considerable experience, and explained 
 to the engineer that the current was going through the arc lamps 
 in the wrong direction, making the bottom carbon positive and 
 the top one negative. 
 
Central Station Experiences. 
 
 "What's the odds, so long as they burn ? Might as well let her 
 rip until morning," said the engineer. 
 
 *^Good Lord, man; you'll burn up all my carbon holders. Can't, 
 you change your plugs on the board?" 
 
 The engineer felt shaky, but he didn't wish to appear too 
 green, so he sauntered over to the switchboard, followed by the 
 trimmer. 
 
 "Yes," he said, with assumed composure, "I s'pose I might." 
 
 The board was a simple affair, consisting of two plugs at the 
 
 ends of flexible cords leading from the circuit lightning arresters, 
 and two sockets connected with the terminals of the dynamo, as 
 shown by the diagram in Fig. i. This arrangement, Jones had 
 explained, was better than connecting the plugs to the dynamo 
 and the sockets to the circuit, because if the plugs should be 
 hanging free at any time when the dynamo was running, their 
 touching each other could not hurt the dynamo. If they were 
 the dynamo connections, touching them together would short- 
 circuit, and might damage, the machine. 
 
 "All you've got to do," suggested the trimmer, who wouldn't 
 have tried to do it for the whole plant, "is to reverse them plugs. 
 
A Defective Arc Lamp. 
 
 That'll make the positive side negative and the negative side 
 positive." 
 
 The engineer pretended to ignore the trimmer's friendly advice, 
 as though it were unnecessary, but he heeded it. Without stop- 
 ping the engine he closed the field switch on the dynamo, "kill- 
 ing" the field, as Jones had shown him should be done when it 
 was desired to open the circuit for any reason. Then he took 
 out the switchboard plugs and reversed them in the holes, went 
 
 "The lamps are all upside down 
 
 back to the dynamo and opened the field switch. The pilot 
 lamp over the dynamo did not light up and the engineer felt a 
 shiver of apprehension pass up his spine. 
 
 "What have you done now?" asked the trimmer, ready to lay 
 all the blame for any possible mishap upon someone else. 
 
 But the engineer kept his head; although he didn't know what 
 was wrong, he did know that he had done nothing to cause any 
 
Central Station Experiences. 
 
 serious trouble. So he determined to simply start up all over 
 again, just as he had at lighting-up time. 
 
 ''Nothing," he replied to the trimmer, ''but I think I'll shut 
 down and take a look at her." 
 
 Accordingly he shut down the engine, took out the switch- 
 board plugs and gave them to the trimmer to hold in proper po- 
 sition for insertion, so as to avoid getting the polarity mixed up 
 again, and pretended to examine the dynamo for a moment. 
 
 "I think she'll go now," he said, without changing a single 
 adjustment, but being careful to see that everything was in its 
 usual condition for starting. 
 
 Then he started the engine, went to the board and taking the 
 plugs from the trimmer put them, one at a time, in the sockets. 
 When the second plug went home the pilot lamp struck its arc 
 with a clack and a hiss that gave the engineer's mind mighty 
 relief. 
 
 "Thought that would fetch her," he said carelessly, and he 
 immediately rose several points in the trimmer's estimation. 
 
 The lamps were now all right, except one that the trimmer 
 brought in burned up the next morning, and matters went along 
 smoothly up to Jones' next visit. The engineer related the whole 
 occurrence to Jones. 
 
 "You opened the field switch while the plugs were in and got 
 no light?" he asked. 
 
 "Yes." 
 
 "And you stopped the engine and started up with the plugs out, 
 putting them in after the machine was up to speed?" 
 
 "Yes." 
 
 "Burn up any lamps?" 
 
 "One." 
 
 "Ah! Let me see it." 
 
 "It's gone to the factory for repairs." 
 
A Defective Arc Lamp. 
 
 "Well, it doesn't matter. Give me a piece of chalk." This 
 was furnished and Jones drew a rough diagram on the floor, like 
 Fig. 2. 
 
 "Suppose D is your dynamo and the crosses represent arc 
 lamps in the circuit. The big cross means a faulty lamp in which 
 the clutch was sticky and the cut-out defective." 
 
 "The one that burned up?" 
 
 "Yes. If you had it here you would no doubt find that there 
 was trouble with both the clutch and the cut-out. The chances 
 are that someone neglected to connect the cut-out, or it has be- 
 come disconnected since the lamp was sent out." 
 
 "What did that have to do with the dynamo not 'picking up?' " 
 
 "Well, you know what the cut-out in a lamp is for, don't you ?" 
 
 •TH- I- 
 
 
 
 <P^'3- 
 
 "To cut it out of circuit when it gets out of order." 
 
 "Yes. Now you know that there are two magnet coils in a 
 lamp." 
 
 "Yes, but I don't know why." 
 
 "I'll tell you. The one with coarse wire draws the carbons 
 apart and the one with fine wire draws them together. The 
 circuits in the lamp are roughly like this," and Jones drew Fig. 3. 
 "5 is the heavy wire coil and s is the fine wire. C and c are the 
 carbons. Now the current divides as long as the lamp works 
 properly; most of it goes through vS" and the carbons and a little 
 goes around through .?." 
 
 "What makes it divide unequally?" 
 
 "The resistance of each path. Do you know Ohm's law?'* 
 
6 Central Station Experiences. 
 
 ''The current equals the voltage divided by the resistance." 
 
 ''Exactly. Now if the path through 5" and the carbons has a 
 total resistance of 5 ohms, and the voltage from T-\- to T — is 45 
 volts, how many amperes will go through ?" 
 
 "Nine." 
 
 "Good. Now suppose the coil ^ has a resistance of 90 ohms, 
 how much current will go through sf" 
 
 The engineer scratched his head to fight for time. 
 
 "Lemme do it on paper," he finally said. 
 
 "No, you don't need to. Suppose the resistance was 9 ohms 
 and the volts 45, how much current would pass?" 
 
 "Five amperes." 
 
 "Well, now if the resistance is ten times nine the current will be 
 one-tenth of five, which is " 
 
 "One-half." 
 
 "Right. Then we will have, say, 9 amperes through 5 and J 
 ampere through s. This is almost exactly what does flow in 
 practice when the lamp is all right. But if the carbon rod sticks 
 so that the coil 5 can't feed it down, and the cut-out is balky or 
 disconnected, the arc gets longer and longer, so that less current 
 goes through 5 and more through s, heating the latter coil and 
 eventually burning it." 
 
 "But " 
 
 "Wait a moment. When you shut down, this lamp had not 
 been going long enough to cause trouble. But when the current 
 was taken off the line, the carbon rod hung up, and your cut-out 
 took a vacation, leaving the lamp just as the sketch shows it. 
 Now when you tried to start up again the only path through that 
 lamp was the coil s, of very high resistance, so that you got no 
 light." 
 
 "What then?" 
 
 "Well, when you first opened your field switch the dynamo was 
 not excited highly enough to force the full current through that 
 coil, but it would probably have heated it up to the burning point 
 after awhile." 
 
 "Then it wasn't necessary to shut down and start up all over 
 again ?" 
 
 "No, you could have done the same thing by pulling your 
 plugs, waiting a minute or so, and putting them back again." 
 
A Defective Arc Lamp. 
 
 7 
 
 "But what's the difference between opening the field switch 
 with the plugs in and putting the plugs in with the field switch 
 open?" 
 
 "None, ordinarily; but in this case there was. With the field 
 switch closed, the armature will not build up any electromotive 
 force, so that when you closed the circuit with the field "killed" 
 and then opened the field switch, there was no pressure at the 
 brushes. The armature was working up, though, when you 
 shut down, and if you had let the machine stay in it would have 
 broken through the lamp coil in a few moments more." 
 
 "But you said opening the switch first and then sticking the 
 plugs would have been better." 
 
 "Yes. It would have broken down the coil at once without 
 waiting so long." 
 
 "Why?" 
 
 "When you opened the switch with the circuit connected, the 
 machine had no E. M. F. and had to work up through resistance. 
 When you shut down and started up again with the field switch 
 open and the circuit disconnected the dynamo worked up a pretty 
 good E. M. F. in a moment or so, and when you stuck the plugs 
 the shock broke down the fine wire coil and made a short circuit 
 across the lamp, enabling the full current to pass and light the 
 other lamps." 
 
 "I don't quite see it." 
 
 "Well, see here." Jones drew another rough sketch, like Fig. 
 4. "Now if you turn the handle of that screw long enough, it 
 will break the cast iron plate, won't it?" 
 
8 Central Station Experiences. 
 
 ''Certainly." 
 
 "Well, if you hit the plate with a hammer it will take less time 
 to break it, won't it ?" 
 
 "A single blow would do it." 
 
 ''Exactly. Now, the action of the screw toward and upon the 
 c^st iron plate is like that of the dynamo upon the lamp coil when 
 you started the machine with the circuit connected." 
 
 "And the hammer is like the action of the machine when it is 
 started first and then connected with the circuit?" 
 
 "Exactly." 
 
 "I see. But why did Sam (the trimmer) say I'd burn up his 
 carbon holders?" 
 
 "You know the positive carbon is longer than the negative?" 
 
 "Yes, twice as long." 
 
 "Well, it is made so, because it burns out twice as fast. Now 
 if you reverse the current through the lamps, the short carbon be- 
 comes positive and burns up entirely before the long carbon is 
 one-third gone. This leaves nothing to carry the arc but the 
 long carbon and the carbon holder of the burnt out short carbon, 
 and the arc would soon melt the carbon holders." 
 
 "Why does the positive carbon burn quicker?" 
 
 "Because the current passes from it to the negative carbon, and 
 carries a good deal of the positive carbon clear across and de- 
 posits it on the end of the negative carbon, so that the latter is 
 constantly replenished and therefore takes longer to be con- 
 sumed." 
 
EXCESSIVE DROP IN THREE- WIRE CIRCUITS* 
 
 The next time Jones visited Millville he found the engineer in 
 deep distress. 
 
 "I've had to speed up my engines," he explained, "because I 
 couldn't get the voltage on the line up to no, even with the 
 rheostat handle clear over." 
 
 "Any grounds on the circuit?" 
 
 "No; there isn't anything wrong with the circuit, as far as I 
 can see." 
 
 "Belts stretched much ?" 
 
 "I've tightened them up all I can without heating the pulley 
 bearings." 
 
 "There are no such things as 'pulley bearings.' " 
 
 "Well, you know what I mean." 
 
 "Yes; but don't get into using careless expressions. Say 'back 
 bearings,' if you choose; that's bad enough." 
 
 Jones walked over to the switchboard and found the pilot lamps 
 burning brightly and the instruments in normal condition, but 
 noticed that the wires leading to one of the voltmeters had been 
 rearranged. 
 
 "Why did you change those wires?" 
 
 "The thing got cranky and wouldn't read " 
 
 "I never saw a voltmeter that could read. Mine simply in- 
 dicates; it hasn't learned to read yet." 
 
 "Well, it wouldn't indicate, and I thought it might have got 
 polarized or something, so I reversed the connections and it went 
 all right." 
 
 "Oh, it did, eh ? Now put them back as they were." 
 
 "But it won't re — indicate that way." 
 
 "Never mind; change them back again." 
 
TO 
 
 Central Station Experiences. 
 
 The engineer did so, and exclaimed triumphantly: 
 'T told you it wouldn't indicate." 
 *'Yes, you did; but it's indicating as hard as it can," 
 The engineer gazed stupidly at the voltmeter and then at 
 Jones. 
 
 'T don't see it move," he said. 
 
 "Look closer and you will see the needle jammed against the 
 back-stop, trying to get away from the scale." 
 This was verified by a close inspection. 
 
 "Now, do you know what is wrong?" 
 "No." 
 
 "The voltmeter needle goes over the 
 scale when you reverse the connections, 
 doesn't it?" 
 "Yes." 
 
 "Then don't you see that the current is 
 going through it in the wrong direction 
 now?" 
 
 "I suppose so, but how can a continuous 
 current change its direction?" 
 
 "It can't. But your dynamo can reverse 
 and change its positive brush into nega- 
 tive, and it has done it." 
 
 The engineer glared resentfully at the 
 offending dynamo and was speechless. 
 
 "When you shunt down to-night," said 
 Jones, "adjust your engine governors like 
 they were originally and reverse the main wires leading to this 
 dynamo. Leave this voltmeter connected as it was at first, and 
 you will find things all right at starting time." 
 
 "But " 
 
 "I'll be back during the day to-morrow, and we can make 
 a test beforehand, if you like." 
 
 The next afternoon Jones returned and found the governors 
 and voltmeter connections restored to their original condition. 
 
 "While we are waiting for starting time to come," he said, "I'll 
 show you what your trouble was," and he drew from his pocket 
 a sheet with several diagrams printed on it. "I had these made 
 for just such a case as yours. Fig. i is a diagram of a simple 
 
 Fig.1 
 
Excessive Drop in Three-Wire Circuits. 
 
 II 
 
 three-wire system where there are no branches — ^just three 
 straight Hne-wires with the load near one end and the dynamos 
 at the other. Now, suppose each circle between the outside and 
 neutral wires passes lo amperes; there are six circles between the 
 positive, P, and the neutral, w, and five between the neutral and 
 the negative wire, A^." 
 
 "So that the load from positive to neutral is 60 amperes and 
 from negative to neutral is 50 amperes ?" 
 
 The engineer glared resentfully at the offending dynamo. 
 
 "Exactly. Now, 50 amperes go straight across from the 
 positive, P, to the negative, N ; what becomes of the other 10 
 amperes that went from dynamo B out along the positive wire ?'* 
 
 "It comes back through the neutral wire." 
 
 "Right. You repeated Ohm's law to me once; can you write 
 it in symbols?" 
 
 "Yes," and the engineer wrote: 
 
 E 
 
12 
 
 Central Station Experiences. 
 
 "Now write it another way." 
 The engineer wrote: 
 
 E 
 
 '*Yes; now the third form." 
 The engineer wrote E = C X R. 
 
 "Good. Now look at Fig. i. If the resistance of P from b to D 
 is -^j of an ohm, how many volts will be used in forcing 60 
 amperes through it?" 
 
 "Sixty times -^^, or 2 ^\ volts." 
 "Right. And if N is the same resistance 
 from a to D, how many volts are lost there ?" 
 "Fifty times -^-^, or 2 volts." 
 "Then it takes some E.M.F. to force the 
 extra 10 amperes back through the neutral, 
 n. Suppose the resistance of the neutral is 
 Jq ohm from / to D, how many volts are 
 lost there?" 1^ 
 
 "10 times ^^, or I volt." 
 "Now add up these losses between a, J, b 
 and D/' 
 
 The engineer did so, and said: 
 "5t'o volts." 
 
 "Right. This is not the total loss, because 
 the wiring from a^ J, b to the dynamos is left 
 out. We will neglect that, though. Now 
 look at Fig. 2 ; see anything wrong about it?" 
 "The outside wires are both positive." 
 
 "Yes; so the neutral is not neutral at all, but has to serve as a 
 negative return wire for both of the outside wires P, P. This is 
 because dynamo A is reversed." 
 "Like mine was ?" 
 
 "Just exactly. Now, assume the same resistances you had be- 
 fore and figure up the loss with 50 amperes in one outside, 60 in 
 the other, and no amperes in the middle wire." 
 
 The engineer wrote 50 X 1-25 = 2 volts. 60 X 1.25 = 2.4 volts. 
 TTO X i-io = II volts. 
 
Excessive Drop in Three-Wire Circuits. i3 
 
 II 
 
 15-^^, volts. 
 
 "15 ^% volts total." 
 
 "Yes. Now your case was worse. Your neutral feeder was 
 designed for only J of the t9tal load instead of f , because all of 
 
 "Your main feeder has a resistance of about j-^ ohm in each 
 balance. What is your load on dynamo No. i ?" 
 
 "209 amperes is the maximum." 
 
 "And on No. 2?" 
 
 "200 amperes." 
 
 ''Your main feeder has a resistance of about -^V ohm in each 
 outside wire and about 1 ohm in the neutral. Figure the losses 
 at 200 and 209 amperes." 
 
 "That means 9 amperes in the neutral, doesn't it?" 
 
 "Yes." 
 
 "Then the loss in the neutral is 9 X i = I2 volts." 
 
 "Well?" 
 
 "The loss in No. i outside wire is 209 times ^V ^^^ '' 
 
 "Add your loads and multiply by^^^." 
 
 "Then it's 409 times j^. That is," after a period of scribbling, 
 "17 volts." 
 
 "Add the neutral wire loss." 
 
 "That makes 18J volts." 
 
 "Therefore your dynamos must give 238^ volts from a across 
 
 to t:' 
 
 "Yes, sir." 
 
 "Now, with No. I dynamo reversed the 209 amperes going 
 out on one outside wire and the 200 going out on the other must 
 come back through the neutral, making 409 amperes in that wire. 
 Figure the loss." ' . 
 
 "409 times J^," pause and scribbling. "Good Lord, that 
 can't be right." 
 
 "What is it?" 
 
 "68 volts and a fraction in the neutral." 
 
 "That's right. Now the loss in the outside wires must be 
 added." 
 
14 
 
 Central Station Experiences. 
 
 "That was 17 volts." 
 
 "Yes, when they were in series; but now they are practically 
 in multiple. Take half the resistance and multiply by the full 409 
 amperes." 
 
 \Vthof409r 
 "Yes." 
 
 "That's a little over 8^ volts." 
 
 "Call it 84; that makes yS^ volts loss; do you wonder that you 
 had to speed up your engines to make that up ?" 
 
 The engineer didn't wonder any longer in this direction, but 
 he did in another. 
 
 "What made the darned thing reverse?" he asked. 
 "There is no telling. There are many things that could cause 
 
 it. When the iron or steel of a dy- 
 namo magnet is extremely soft the 
 machine is likely to excite in either 
 direction for the first few times. A 
 heavy blow will sometimes reduce the 
 residual magnetism so as to make the 
 machine uncertain in exciting." 
 
 "How am I going to tell hereafter 
 whether the dynamos are all right be- 
 fore I put on the load ?" 
 
 "Connect two 120- volt lamps 
 
 across from outside to outside of 
 
 the dynamos (see Fig. 3), and if they light up both dynamos will 
 
 be excited in the same direction. If they don't light up reverse 
 
 the mains at the terminals of one dynamo." 
 
 "Suppose I reverse the wrong machine?" 
 
 "The voltmeters will both throw their needles away from the 
 scale, and you will have to reverse their connections." 
 
 "Won't the change of polarity hurt anything on the circuit?" 
 "Not unless you have arc lamps on your incandescent circuit. 
 Then you must shut down, straighten back the dynamo mains 
 you had reversed, and reverse those of the other dynamo." 
 
 -o 
 
 LAMPS '^-^■'' 
 
 Fig. 3 
 
CARELESS PARALLELING OF DYNAMOS. 
 
 The Alillville factory and shop owners had reahzed the great 
 advantages of electric motors to such a degree that the Httle cen- 
 tral station had accumulated a motor day load of considerable 
 magnitude, necessitating the installation of another dynamo in 
 
 order to avoid working the two 500 lighters day and night. Ac- 
 cordingly, a 230-volt, lOO-kilowatt generator had been put in and 
 a separate motor circuit established. Then the lamp load gradu- 
 ally increased until, for an hour or so early in the evening, the 
 two 115-volt machines were slightly overloaded. In order to re- 
 lieve this overload it was the custom to couple the motor circuit, 
 
i6 
 
 Central Station Experiences. 
 
 which was not fully loaded, with the outside legs of the three- 
 wire system, operating the whole as one system, as shown dia- 
 grammatically in Fig. i. The voltmeters were provided with 
 voltmeter switches (not shown) whereby each could be connected 
 with the pressure-wires, the bus-bars or the dynamo brushes. 
 These connections are omitted for clearness. 
 
 The 230-volt dynamo and its circuit were operated all day, and 
 at dusk the three-wire system was started up and coupled, by 
 means of the switch S, to the 230-volt system. The manipula- 
 tion of this switch and the adjustment of the 
 dynamos was entrusted to Sam, the trimmer, 
 the engineer standing by the throttle until 
 everything was working smoothly. Repeated 
 success in "bunching" the circuits developed 
 an overconfidence and carelessness in Sam 
 which one evening caused the addition of sev- 
 eral gray hairs to the engineer's stock and 
 almost wrecked the dynamos. 
 
 On the occasion referred to the engineer 
 had brought the two smaller machines up to 
 speed and was standing at the throttle of their 
 engine when Sam closed the switch S con- 
 necting the two circuits. There was an omin- 
 ous screech that chilled the engineer's blood, a 
 sputtering and flashing at all of the brushes^ 
 a yell of "Stop her! stop her!" from Sam, 
 and two reports like musket shots as the fuses 
 Power,N.r. of thc ii5-volt dyuamos blew, followed in- 
 stantly by those of the larger machines — all of these occurrences 
 being so nearly simultaneous that there was no opportunity to do 
 anything but gasp. 
 
 The engineer felt weak in the knee-joints as he rushed over to 
 the switchboard. The machines were all running as peacefully as 
 lambs, but the circuits were of course dead, the fuses being gone. 
 "What in h — 1 did you do ?" demanded the engineer. 
 Sam's self-assertiveness bristled. 
 
 "Didn't do nothin' but shut the switch," he snapped out. 
 "You must have done something wrong; they never cut up 
 that way before." 
 
 "Well, I guess I know how to bunch 'em." 
 
Careless Paralleling of Dynamos. 
 
 17 
 
 The eng-ineer said no more, but, profiting by his last experience, 
 began a minute examination of the switchboard. Nothing seemed 
 wrong except the mehed fuses ; both of the pilot lamps across the 
 terminals of the 115-volt dynamos were burning brightly, and the 
 230-volt pilot lamp on the large machine was also burning, though 
 not so brightly as the other two. Then the engineer switched his 
 voltmeter over to the terminals of the big machine; it indicated 
 228. He next switched it to the pilot lamps of the two small ma- 
 chines ; it indicated 240 ! 
 
 'Tt's about time you knew better than to switch 240 volts on to 
 228," he remarked caustically. 
 
 "Stop her! Stop her!" 
 
 'T didn't," said Sam, determined to evade all responsibiUty. 
 "'Them little machines have raised since they warmed up." 
 
 "Hello, here; what's up?" and Jones' cherry face appeared in 
 the doorway. 
 
 The engineer recited hastily the occurrences. 
 
 "All right," said Jones; "shut down your engines, open all your 
 switches, and put in fresh fuses." 
 
 While the fuses were being restored, Jones made a close ex- 
 amination of the dynamos by the aid of a 45-volt incandescent 
 lamp connected in shunt to one of the station arc lamps (see 
 Fig. 2). The commutators were blackened and burned a little, 
 but sandpaper soon corrected this and in a very few minutes all 
 of the machines and circuits were in operation again. 
 
1 8 Central Station Experiences. 
 
 ''Now, tell nie more about it," said Jones. 
 
 "There isn't anything more to tell," said the engineer. "I told 
 you exactly what happened." 
 
 '"'Who worked the switchboard?" 
 bam. 
 
 "Did you examine the board afterwards ?" 
 
 "Yes; nothing was wrong except that the voltmeter showed 
 240 on the small machines and 228 on the big one." 
 
 Jones grinned and then looked savage. 
 
 "Where's that d— d fool ?" 
 
 "Sam? He's gone. He said the little machines raised their 
 voltage after they warmed up." 
 
 "He did, did he? Well, you tell him for me that he's an ass." 
 Just then Sam came in, with his arrogance all restored. "Hi, 
 come here," called Jones. 
 
 Sam came, smiling. 
 
 "So the little machines raise their voltage when they warm up, 
 do they?" 
 
 Sam's smile evaporated. 
 
 "Y-yes, sir; I mean — no — yes " 
 
 "I suppose so. When you get time, read some electrical 
 primer, and you'll find that wire increases its resistance when it 
 heats, so that a field magnet coil has less current in it warm than 
 cold, and the voltage of the machine is lower when the machine 
 is warm than when it's cold." 
 
 "Yes, sir; of course, but " 
 
 "Shut up. Why didn't you use the voltmeter before you 
 threw the small machines in circuit?" 
 
 "The pilot lamps looked all right, sir," very meekly. 
 
 "Oh, they did? Anddo you think you'd look all right if I told 
 the chairman you nearly wrecked the station because you were 
 too lazy to use the voltmeter switch ?" 
 
 "Please sir " 
 
 "No, I'm not going to tell on you this time, but hereafter you'd 
 better follow your instructions and wait for your judgment to 
 ripen." 
 
 Sam vanished in the night air with not a trace of swagger. 
 
 The engineer turned to Jones with an air of interrogation. 
 
 "Perfectly simple," said Jones. "Here is what you had just 
 
Careless Paralleling of Dynamos. 
 
 19 
 
 before the switch was closed between the circuits," and he made 
 the sketch shown by Fig. 3. "Now when the switch was closed, 
 the connections shown by the dotted lines a and b were made." 
 
 "Yes." 
 
 "Then the difference of 12 volts between the two circuits forced 
 current through the big armature and the series field coil back- 
 wards, and the big machine was driven as a motor." 
 
 "Backwards?" 
 
 "No, in the same direction, because the shunt field magnetized 
 
 ^4o volts 
 
 Or^ 
 
 FIG. 3. 
 
 in the same direction as before. The current in the series field 
 
 was reversed though, as indicated by the dotted arrow, and this 
 
 weakened the field magnet." 
 "What effect did that have?" 
 "Increased the speed of the machine." 
 "Does a motor run faster with a weakened field?" 
 "Yes; up to the point where the field is too weak to pull over 
 
 the armature." 
 "Why?" 
 
20 Central Station Experiences. 
 
 •'Because the back E.M.F. of a motor armature must equal 
 the E.M.F. appHed at the brushes, mimis the volts lost in the 
 armature, and its value depends upon speed and field magnetism 
 If the field weakens, the motor speeds up to maintain its back 
 E.M.F. at the proper point." 
 
 "Then why should there have been any trouble? Why didn't 
 the big dynamo simply speed up to make up for the weakened 
 field?" 
 
 'Tt did try to, but it had to drag the engine with it; besides, it 
 couldn't change its speed in an instant, even without the engine, 
 and before it reached the high speed necessary to make its back 
 E.M.F. good the fuses blew." 
 
 The engineer scratched his head in a puzzled fashion. 
 
 "I don't exactly see why the fuses should have blown." 
 
 ''You see that there was an excess of 12 volts between the two 
 circuits, don't you ?" 
 
 "Yes." 
 
 "Well, ignore the outdoor circuits and consider the dynamos 
 connected together." 
 
 "Well?" 
 
 "The resistance of the big armature and the series coil to- 
 gether is about Y^ ohm ; now when the switch was closed 
 the E.M.F. of 228 volts from the big armature opposed 228 volts 
 of the 240 generated by the two small armatures, leaving 12 volts 
 opposed by nothing but wire resistance." 
 
 "The ^ of an ohm ?" 
 
 "That added to the resistance of the small armatures and the 
 intermediate connections. These amounted to approximately 
 rlo^ or -^\ ohm, so the total resistance through the three 
 armatures, etc., was " 
 
 "Forty-three thousands of an ohm." 
 
 "Yes. Now see how much current 12 volts can drive through 
 forty-three — make it fifty thousandths for heating and good 
 measure; fifty thousandths or one twentieth of an ohm." 
 
 The engineer scribbled on the back of his memorandum book 
 and then looked up in surprise. 
 
 "That can't be true," he said; "it isn't enough to hurt any- 
 thing." 
 
 Jones smiled. "How much was the first rush?" 
 
Careless Paralleling of Dynamos. 2i 
 
 The engineer showed him these figures: 
 .05) 12.00 (240 
 
 TO 
 
 20 
 20 
 
 "Two hundred and forty amperes?" 
 
 "That's what it figures out." 
 
 "Precisely; but that state of affairs lasted less than one second. 
 Then your series field coils had neutralized enough of the excit- 
 ing power of the shunt coils to cut down the total field about 
 40 per cent, reducing the E.M.F. of the big armature to 60 per 
 cent of its first value — what is 60 per cent of 228?" 
 
 ''One thirty-six and eight-tenths," after some scribbling. 
 
 "Call it 137 for even figures; that leaves how much unbalanced 
 voltage?" 
 
 "137 from 240 — 103 volts." 
 
 "Now see how much current 103 volts will force through ^f^- 
 ohm?" 
 
 The engineer divided 103 by 0.05 and said: 
 
 "Nearly 2,100 amperes." 
 
 "Yes; but it is probable that the fuses blew before it got any- 
 where near that, or you wouldn't have any dynamo left." 
 
 The engineer seemed absorbed. 
 
 "What's worrying you now?" 
 
 "I was only wondering where it would stop. As the reversed 
 current increases, the series coils get stronger in the wrong direc- 
 tion and weaken the field more and more, and " 
 
 "Yes, but your armature speeds up and increases the back 
 E.M.F., so that the current doesn't go up by jumps, but with a 
 sort of swoop. If the armature had no weight, so that it could 
 change its speed the instant the field weakened, there would be 
 no increase in the current, but the speed would increase until the 
 back E.M.F. equalized the incoming E.M.F. (minus the 'drop') 
 under the weakened field." 
 
 "What was the awful screeching?" 
 
 "The belts all slipping around the pulleys, due to the sudden 
 overload on all the machines." 
 
 "Whv haven't we had this trouble before?" 
 
2 2 Central Station Experiences. 
 
 "Because Sam tried the E.M.F. of the machines with the volt- 
 meter before he threw them together. There isn't the slightest 
 danger, if one uses the voltmeter and a little horse sense. The 
 safest plan is to let the small dynamos lack a volt or two of the 
 E.M.F. of the compound-wound machine when you couple them. 
 Then the big dynamo will take a little more than its own load 
 and help the others out." 
 
A '^DEAD'^ DYNAMO AND HOT FIELD COILS. 
 
 Several months later Jones, on one of his frequent visits to the 
 Millville Station, found the engineer sitting on the floor near one 
 of the small dynamos, his face and hands bearing grimy evidence 
 of unusual toil, and a despondent air being obtrusively manifest. 
 
 ''Well, tell me all about it," he said, appropriating a small tool- 
 chest for a seat. 
 
 "She's as dead as a door-nail," said the engineer, indicating 
 by a disgustful wave of a monkey wrench the near dynamo. 
 
 "Since when?" 
 
 "Stopped generating an hour or so before shutting down time 
 this morning," 
 
 "Were you here?" 
 
 "No; the boy called me." 
 
 "What did you do?" 
 
 "Started up the 220-volt machine and put it across the outside 
 legs and then put a bank of lamps between the neutral and the 
 light load side to balance." 
 
 Jones arose and whacked the engineer on the back enthusiasti- 
 cally. "Good boy," he said. "Now tell me about the lame duck." 
 
 "Break in the field circuit somewhere." 
 
 "How do you know?" 
 
 The engineer looked injured. 
 
 "Why, I tested to see, of course," he replied. 
 
 "How?" 
 
 "Connected the field circuit with the good machine to charge 
 it, but it wouldn't give a spark. You see, I thought it had lost its 
 magnetism." 
 
 "And you could get no current through the field circuit ?" 
 
 "Not a bit." 
 
24 
 
 Central Station Experiences. 
 
 "^Had any trouble with it lately?" 
 
 ''None to speak of. I noticed that three of the coils ran warmer 
 than the fourth one for a day or so, but not warm enough to 
 hurt." 
 
 ''Rheostat heat up unusually?" 
 "I didn't notice that." 
 
 "Get me enough lamp-cord to reach from the dynamo to the 
 switchboard, with six feet to spare, and put a lamp socket on one 
 end of it and an attachment plug on the other. And bring a 
 pair of those extra plugs from the arc switchboard." 
 
 This was done, and Jones proceeded to cut 
 - one conductor of the lamp-cord about four feet 
 from the lamp socket and untwist the con- 
 ductors for a couple of feet on each side of the 
 break. Then he fastened the ends of the sev- 
 ered conductor to the switchboard plugs, trans- 
 ferred one of the pilot lamps of the 220-volt 
 machine to its socket, and screwed the attach- 
 ment plug into the pilot lamp socket. The re- 
 sult was an arrangement like that shown in Fig. 
 I. Obviously, a connection between the plugs 
 would cause the lamps to light up. 
 
 "Now disconnect your rheostat wires." 
 The engineer did so. 
 "Hold them against these plugs." 
 The engineer obeyed, and the lamps remained 
 dark 
 
 "Open in the rheostat circuit somewhere. Why didn't you try 
 that before?" 
 
 The engineer simply looked sheepish. 
 
 Jones went to the switchboard and applied the plugs to the 
 terminals of the rheostat, but no light resulted. 
 "Turn the handle," he said. 
 
 The engineer turned the rheostat arm, and when the contact 
 finger touched the third button from the "all-out" position the 
 lamps lighted. The engineer heaved a sigh of relief. 
 
 "Don't be in a hurry; you're not out of the woods yet," said 
 Jones grimly. 
 
 Fig.1. 
 
A "Dead" Dvnnmo and Hot Field Coils. 
 
 25 
 
 "It's easy enough to 'bridge over' that break," said the en- 
 gineer. 
 
 "Yes, quite simple; but that's only the beginning. There's a 
 short circuit in one of your field coils." 
 
 The engineer stared in amazement. 
 
 "How do you know that?" he asked. 
 
 Jones grinned. "That coil that ran so beautifully cool is either 
 cut out entirely or has a short circuit that cuts out most of it." 
 
 "Then the other three ran hot because they were doing all the 
 work ?" 
 
 Jones nodded and walked over to the affected dynamo. 
 
 "Which coil ran cool?" he asked. 
 
 The engineer indicated the left-hand upper coil, which Jones 
 
 proceeded to uncouple from its mates. Then he attached to the 
 hand plugs of his testing arrangement (Fig. i) the ends of a 
 length of flexible cord leading to the low scale terminals of a 
 portable voltmeter which he habitually carried, and placed the 
 voltmeter on the floor. 
 
 "Take the readings/' he said to the engineer. 
 
 Then he applied the plugs to the terminals of the suspected 
 coil. "What is it?" he asked. 
 
 "Nothing," replied the engineer. 
 
 Jones applied the plugs to the terminals of another field coil. 
 "Now," he said. 
 
 "One and four-tenths volts." 
 
 "Now," repeated Jones, touching the terminals of a third coil 
 ivith his plugs. 
 
26 
 
 Central Station Experiences. 
 
 "One and three-tenths." 
 
 "Once more," and he touched the fourth coil's ends. 
 
 "One and four-tenths." 
 
 "Pretty close results," commented Jones. "That cold-blooded 
 coil is entirely short-circuited; the other three are all right." 
 
 "What's to be done?" 
 
 "Lift off the upper half of the field magnet and take out the 
 coil." 
 
 With the aid of a portable, or rather movable, gallows crane 
 this was soon accomplished, and Jones quickly stripped the in- 
 sulation off the sides of the coil whence the terminals issued. 
 
 "Thought so," he muttered, as he exposed the end of the coil 
 across which the starting end was led outward. A charred spot 
 
 Power, X.Y. 
 
 at the outer edge (A, in Fig. 2) showed the location of the trouble. 
 
 "What made it burn there?" asked the engineer. 
 
 "The vibration of the machine caused the terminal wire to rub 
 through the insulation, and the current simply went across from 
 the starting end to the outside turn instead of going through the 
 coil." 
 
 Jones pried the end layers apart gently with a dull-pointed 
 screwdriver and stuck a sliver of mica between each pair of layers. 
 Then he varnished the end face of the coil heavily with shellac, 
 let it harden, and then taped the coil, but left the terminal out- 
 side and taped it separately, so that the coil looked like Fig. 3 
 when it was ready to go back in place. 
 
 "Why didn't they fix the end that way at the factory?" asked 
 the engineer. 
 
 "They always do now. That coil must have been taken from a 
 
A "Dead" Dynamo and Hot Field Coils. 
 
 27 
 
 lot made up before they changed the arrangement of the inner 
 terminal. I'll have a new one sent to replace it." 
 
 When the coil had been put back in place Jones applied the 
 hand plugs of his improvised testing outfit to the terminals, and 
 the engineer read the voltmeter indication. 
 
 "One and nearly five-tenths." 
 
 Jones vented his satisfaction in a chuckle. ''Let's try 'em all 
 around again," he said, applying the plugs to the next coil. 
 *'Now." 
 
 "One and five-tenths." 
 
 With the aid of a portable crane the too half was Ifted off. 
 
 "Again." 
 
 "One and four-and-a-half." 
 
 "Last coil." 
 
 "One and five." 
 
 "Good as gold," said Jones. "Let her down again." 
 
 The engineer lowered the suspended half of the field magnet, 
 Jones guiding it into place, and the machine was soon running 
 as placidly as ever. 
 
 "Why were the last voltmeter readings higher than the first 
 ones?" asked the engineer. 
 
28 Central Station Experiences. 
 
 "Because your load on the motor circuit happened to be 
 heavier and the E.M.F. at the switchboard was higher." 
 
 "Well, what did those readings indicate, anyhow?" 
 
 "Only the comparative condition of the coils. As long as the 
 voltmeter indications were the same, or practically the same, it 
 was safe to assume that the coils were of equal resistance. It 
 was immaterial what the voltmeter indicated so long as it indi- 
 cated something, and the same something for each coil." 
 
 The engineer did not wholly take in this reasoning, and his 
 face showed it. Whereupon Jones relapsed into diagrams, draw- 
 ing Fig. 4. 
 
 "That is what we had, isn't it?" he asked. 
 
 The engineer admitted that it was. 
 
 "^Now, suppose that the voltage across the bus-bars is 230, and 
 that a current of ^ ampere passes through the circuit. If the coil 
 
 FIG. 4- 
 
 has a resistance of 3 ohms, what will be the voltage at its termi- 
 nals?" 
 
 The engineer wrote 
 
 E = C XR. If C = 1 and i? = 3, then E =: i X 3, or ij. 
 
 "One and a half volts," he answered. 
 
 "Now, suppose the coil had practically no resistance " 
 
 "But that isn't possible," interrupted the engineer. 
 
 "No; but if the ends were connected together by a heavy short- 
 circuit, the resistance from A to B would be inappreciable, and in 
 that case " 
 
 "The voltmeter would be short-circuited and wouldn't indi- 
 cate." 
 
 "Precisely so. Isn't that what we found?" 
 
 "Yes. Suppose only a part of the coil were cut out, what 
 would happen?" 
 
 "Figure it for yourself. With ^ ampere you said the 'drop' in 
 
A "Dead" Dynamo and- Hot Field Coils. 
 
 29 
 
 the coil was i^ volts; that leaves 228^ for the two lamps, cord, 
 and connections, which means a resistance of what?" 
 
 "Two hundred and twenty-eight and a half divided by one-half; 
 four hundred and fifty-seven ohms." 
 
 "Now, if one-third of the coil were cut out by a good solid 
 short-circuit, the resistance left would be " 
 
 "Two ohms." 
 
 "Add this to the circuit resistance of 457." 
 
 "Four hundred and fifty-nine ohms total." 
 
 "And the current flowing, under 230 volts?" 
 
 "Two hundred and thirty divided by four hundred and fifty- 
 seven" — pausing to scribble — "a trifle over half an ampere." 
 
 "And the drop in the damaged coil?" 
 
 "About a volt." 
 
 FIG. 5. 
 
 "Practically two-thirds of the drop in a good coil, showing 
 that about one-third of the coil is cut out." 
 
 "But isn't there some way of getting at it without so much 
 figuring?" 
 
 "Yes. If you wanted to find the actual resistance of a coil and 
 had no Wheatstone bridge, you could rig up a testing outfit this 
 way," drawing Fig. 5. "The extra resistance may be a coil of 
 wire or a iio-volt incandescent lamp of 32 candle-power or over. 
 R is a. dynamo regulating rheostat — as small a one as you can 
 get; A is the ammeter off your arc light switchboard, and F is a 
 voltmeter with a low and a high scale." 
 
 "Why are two resistances necessary?" 
 
 "The extra one may. not be. If R is sufficient to cut down the 
 current to one ampere when the testing terminals T and T are 
 
30 Central Station Experiences. 
 
 together, no extra resistance will be needed. If not, then enough 
 extra resistance must be put in to bring the current down to an 
 ampere when the finger of R is on the last button, or somewhere 
 near it." 
 
 "How do you test with that arrangement?" 
 
 "Connect the terminals, T, T, with the coil, or whatever you 
 wish to test. Adjust the rheostat until the ammeter indicates ex- 
 actly one ampere; then the voltmeter will indicate the resistance 
 in ohms of whatever T and T are touching. These terminals 
 should be clamps if the object tested is of low resistance, so that 
 the resistance at the contacts will be inappreciable." 
 
 Jones was half way to the door, leaving the engineer studying 
 the sketch, before the latter realized his departure. 
 
 "Hey, there," he cried; "wait a minute." 
 
 Jones paused and turned about. 
 
 "When one coil was cut out^ why didn't the E.M.F. of the 
 dynamo drop 25 per cent ?" 
 
 "Because the resistance of the three coils was one-fourth less 
 than that of all four, and the current was therefore one-third 
 greater; three coils passing 12 amperes are equal to four coils 
 passing 9 amperes, if the coils are alike." 
 
 "Oh, yes. But why didn't the dynamo spark like fury with an 
 unbalanced field ?" 
 
 "Because the armature is wound so that each path, from brush 
 to brush, passes under all four poles instead of only one, and all 
 four paths gave the same E.M.F. Good-night." 
 
A ^'BREAKING'' ARC CIRCUIT — SIMPLE GROUND 
 
 DETECTOR. 
 
 ''I'm sure I can't imagine what the devil ails the confounded 
 thing," admitted the engineer^ with a sigh of vexation. 
 
 ''Mebbe the old machine's begun to do like them incandescent 
 dynamos — slack down when she gits warmed up," hazarded Sam. 
 
 The engineer shook his head dubiously. "She wouldn't have 
 run all right up to now and then take on such capers," he said. 
 
 It was the arc light dynamo that worried the men. 
 
 "Did you look over all your lamps last night?" asked the en- 
 gineer. 
 
 "Every last one," averred Sam stoutly, "and they was all as 
 white as snow and fine as silk." 
 
 "Every one — every single lamp ?" persisted the engineer. 
 
 "Yes; every one — leastways every one in reach," with a suddep 
 revival of memory. "You know there's two upstairs in old map 
 Stringer's place that I trim just before he shuts up, and I can't 
 see 'em from outside." 
 
 The engineer looked bored and disgusted. 
 
 "And you've spent a week looking for bad lamps and had me 
 worried half to death, and never thought of those lamps," he ex- 
 claimed. "Bring 'em in right away." 
 
 The lamps were brought in forthwitli and others put in their 
 places, and tliat night the circuit worked worse, if possible, than 
 before. The engineer was in despair the next morning. 
 
 Eater in the day he became suddenly possessed of an idea, and 
 when no one was around he took down one of the station lamps 
 which had been recently hung to illuminate an improvised testing 
 rack and work-bench for arc lamps. That night the circuit be- 
 haved in an orderly and dignified manner, to the intense relief of 
 
32 Central Station Experiences. 
 
 the engineer and the great mystification of Sam, who never 
 learned the secret of the sudden remedy. 
 
 Jones happened along in the course of a few days and the en- 
 gineer promptly carried him ofif to a remote corner and unfolded 
 his tale of distress. 
 
 ''What did the circuit do?" asked Jones. 
 
 ''Burned all right for a time, but got weaker and weaker until 
 about 9 o'clock, when it 'broke' and then started up smoothly 
 again." 
 
 "Burn smooth the rest of the night?" 
 
 "No; it broke that way two or three times during the night." 
 
 "Dynamo fully loaded?" 
 
 "Yes." 
 
 "Regulator 'clear over' at full load?" 
 
 "Yes; but it has a margin after the private lamps are cut out." 
 
 "Then the circuit didn't weaken previous to the breaks that fol- 
 lowed the first one." 
 
 "How do you know that?" 
 
 "Because the reason it grew weak before the first break was 
 that the regulator couldn't strengthen the field of the dynamo 
 any more, the maximum being reached at that time." 
 
 ''Well?" 
 
 "Well, the carbon rod of your defective lamp hung up and as 
 the carbons burned away the resistance of the arc increased. The 
 effect was the same as cutting two or three lamps in circuit, and 
 as the dynamo was giving its maximum voltage and couldn't 
 give any more, the increased resistance cut down the current in 
 the circuit, but it couldn't have cut it down very much." 
 
 "It dropped from 9.6 to 8 amperes." 
 
 "Quite probable. And after the private lamps were cut out it 
 didn't drop at all until the circuit actually broke, because you had 
 some reserve voltage and the regulator took care of the lengthen- 
 ing arc just as it would of an increase in the number of lamps." 
 
 "Why did the lamp hang up?" 
 
 "Something wrong with the feed. Let's look at it." 
 
 The engineer led the way to where the defective lamp was and 
 Jones put it on the bench, removed the box casing and proceeded 
 to examine the mechanism. 
 
A ''Breaking' Arc Circuit — Simple Ground Detector. 33 
 
 When no one was around he took down one of the station lamps. 
 
34 Central Station Experiences. 
 
 **Why, the lamp hasn't any automatic cut-out in it," he ex- 
 claimed. 'Who took it out?" 
 
 The engineer colored and looked abashed. "I took it out to 
 replace a damaged cut-out in a street lamp," he explained. 
 
 ''That's all right, but you shouldn't allow this lamp in circuit 
 anywhere in that condition." 
 
 "I know it, but I thought being right here in the station we 
 would notice anything, wrong with it and cut it out." 
 
 Jones grunted derisively and proceeded with his examination 
 of the lamp. 
 
 "Shunt coil disconnected and arc-strike too short," he an- 
 nounced. "You must have jabbed the shunt coil terminal when 
 you took out the cut-out." 
 
 The engineer was speechless with mortification. Jones grinned 
 reassuringly. 
 
 "Never mind," he said, with his usual cheery air restored, 
 "everybody makes blunders, and you'll know better next time," 
 w^hich comforted the engineer somewhat. 
 
 "What efifect did the adjustment for striking a short arc have?" 
 he asked. 
 
 "Rather a beneficial one as it happened. The lamp struck a 
 very short arc so that it took longer for the carbons to burn away 
 until the arc broke than if the regular size arc had been struck." 
 
 "And the reason the carbon rod hung up was that the shunt 
 coil was disconnected and could not work the feed?" 
 
 "Precisely so. The series coil simply lifted the rod with a bang 
 and held it there until the carbons burned away and opened, the 
 circuit." 
 
 "You see," said the engineer apologetically, "I don't stay 
 around after nine o'clock much, and the boy is around the dyna- 
 mos and never comes over to this corner. 
 
 "All the more reason for having a good lamp here," said Jones, 
 dryly. "You can put it down as a safe rule that no apparatus is 
 too good for station use, so far as the vital working parts are 
 concerned. You can use lamps and other things in the station 
 that don't present a good enough appearance for a customer, but 
 the 'works' should be in apple-pie order. The practice of using 
 damaged switches, blackened incandescent lamps, defective arc 
 lamps," with a sly twinkle, "and such things, around any plant 
 
A '^Breaking" Arc Circuit — Simple Ground Detector. 35 
 
 is a most short-sighted one. Another thing — whenever you have 
 any circuit trouble always begin to look for it in the station." 
 
 This little homily delivered, Jones changed the subject. 
 
 "How are your circuits; all fairly loaded?" 
 
 "The iio-volt circuits have considerable margin since I 
 changed some of the motors to 220 volts." 
 
 "Better displace five of your private arc lamps on the arc circuit 
 with five constant-potential arc lamps on the iio-volt circuits. 
 Then your arc dynamo will have a reserve E.M.F. and the regu- 
 lator can take care of long arcs or other demands for more volt- 
 age." 
 
 The engineer signified his acquiescence and fidgeted around 
 uneasily for a few moments. 
 
 "Well, what's troubling you now?" asked Jones, amused by 
 his sheepish expression of countenance. 
 
 ■DYNAMO TERMINALS 
 
 — O C^ 
 
 FIG. 1. 
 
 "I want to make a ground detector and tester for the arc 
 circuit." 
 
 "That's simple. Get twenty-five lOO-volt incandescent lamps, 
 8 candle-power each, a rheostat face with twenty-four contact 
 buttons, a double-pole knife-switch for high potential, and a coil 
 of fine German silver wire of high enough resistance so that when 
 your 600-volt portable voltmeter is connected in series with this 
 coil across your dynamo terminals like this" (Fig. i), "the volt- 
 meter needle will not go beyond the scale. Then arrange your 
 things this way," drawing a diagram like Fig. 2. 
 
 "How do you use it?" asked the engineer, a little doubtfully. 
 
 "Close the switch and carry your rheostat handle from one ex- 
 treme to the other. If the voltmeter needle doesn't move at all, 
 there is no ground. If it indicates at any part of the rheostat 
 
36 
 
 Central Station Experiences. 
 
 travel, move the handle until you reach a button where the volt- 
 meter needle shows the lowest indication — zero, if you can get it 
 so low. Then the ground on your circuit will occupy the same 
 position with relation to the arc lamps that your rheostat finger 
 does to the incandescent lamps." 
 
 The engineer seemed a little dazed. 
 
 "See here; suppose you have fifty arc lamps in circuit and 
 twenty-five incandescents in your detector, then " 
 
 'T see," broke in the engineer, "each incandescent lamp would 
 represent two arcs and the position of the rheostat finger in the 
 string of incandescents would correspond with the position of the 
 ground on the circuit of arcs." 
 
 "Exactly so. If the voltmeter indicated zero (or minimum) 
 
 Q CIRCUIT O 
 TERMINALS 
 
 FIG. 2. 
 
 when the rheostat finger was between lamps Nos. 7 and 8, count- 
 ing from left to right, the ground on the line will be found be- 
 tween the 14th and tjie i6th arc lamps, counting from the left- 
 hand end of the circuit." 
 
 "Suppose there are two grounds on the circuit ?" 
 "Then all the lamps between the two grounds will burn either 
 very weak or not at all, and the ground detector will act as though 
 there were just one ground midway between the two that really 
 exist." 
 
A "Breaking" Arc Circuit — Simple Ground Detector. ^j 
 
 "Then if there were two grounds, one at lamp No. 2y and one 
 at No. 33^ the ground detector would mdicate one ground near 
 lamp No. 30?" 
 
 "Exactly. And your lamps from No. 2y to No. 30 would either 
 be out or very red and weak." 
 
ANOTHER CASE OF ^'DEAD'' DYNAMO. 
 LOW VOLTAGE. 
 
 — 220-VOt-TS 
 
 Fig.1. 
 
 ''I swear I've a good mind to throw the cussed machine in the 
 canal," sputtered the engineer, wrathfuUy glaring at the 250-volt 
 dynamo. The dynamo manifested no concern as to its impend- 
 ing doom, but lay there innocently, "dead to the world" in gen- 
 eral and to its own circuit in particular. 
 
 It's the second time I've had trouble with 
 it inside of three months," continued the solilo- 
 quizer, '' and I'm worn out." 
 
 Sam shifted to the other leg and looked sym- 
 pathetic, but vouchsafed no audible condolence. 
 
 "Go telephone Jones to come over right 
 away. He's at Centerville to-day." 
 
 Sam went, and Jones appeared within an 
 hour. The engineer's temper had effervesced 
 and he presented the case more calmly. 
 
 "Won't generate?" said Jones. "What did 
 you find?" 
 
 "Nothing ; that's what's worrying me." 
 
 "Field circuit test up closed?" 
 
 "Yes ; rheostat and all. And there is no 
 
 ' rower, JS.r. 
 
 ground." 
 
 Jones scratched his head and looked thoughtfully at the 
 dynamo. 
 
 "Sure about the ground?" 
 
 The engineer didn't reply, but stepped over to the dynamo and 
 applied the terminals of his testing arrangement (Fig. i) to one 
 field terminal and the frame of the dynamo; the lamps remained 
 dark. 
 
Another Case of ''Dead'' Dynamo — Low Voltage. 39 
 
 "Try the field circuit again," said Jones. 
 
 The engineer touched the shunt field terminals (the brushes 
 were raised from the commutator) with the plugs and the lamps 
 glowed, but were dull red. 
 
 "Poor circuit," said Jones. "Looks as if there was a bad con- 
 nection somewhere," 
 
 As he spoke the lamps went out, and the engineer looked 
 blankly at tlie dynamo and then at Jones. The latter worthy 
 merely grinned with an irritating degree of cheerfulness. 
 
 "What in the " began the engineer, still pressing his field 
 
 plugs against the field terminals. 
 
 "Don't. The fish won't bite," said Jones. "You have a broken 
 connection somewhere; test the field coils separately." 
 
 The engineer removed the tape from the connecting clamps be- 
 tween the field coils and applied one test plug to the upper field 
 
 terminal and the other to the clamp on the other side of the near- 
 est coil (a, in Fig. 2). The lamps burned brightly. Then the 
 rheostat terminals, b, c, were touched with the plug, with the 
 same result. So also as to d, but when the plug was applied to 
 the lower field terminal the lamps were dark. 
 
 "Broken between the last clamp fd) and the terminal block," 
 said Jones. "Look for a short bend in your connecting wires." 
 
 Sure enough, further investigation revealed that the lead, e, 
 which was a small stranded cable, was broken inside the insula- 
 tion at a point where it was bent at a sharp angle to turn upward 
 to the terminal block. The ends presented a peculiar appearance, 
 being of a dull brownish-yellow and rounded. 
 
 "Why do the cable ends look that way?" asked the engineer. 
 
 "Burnt," said Jones. "Part of 'em broke and the others burned 
 in two." 
 
40 Central Station Experiences. 
 
 ''Why didn't the machine excite when the circuit tested up 
 closed?" 
 
 ''Because there was probably the merest contact between the 
 ends of one broken strand, and this was of such high resistance 
 that sufficient current to excite couldn't get through." 
 
 "But enough current passed to light the lamps," said the en- 
 gineer. 
 
 "Yes, to a measly dull red. About a third of an ampere passed. 
 If you had raised the brushes and thrown the field in circuit, the 
 remaining contact inside the insulation would have burned away 
 instantly, instead of sizzling itself in two when your test lamps 
 were in series with it." 
 
 "What broke the strands of the cable first?" 
 
 "Yanking it up and down when the boy wiped off the machine. 
 Now, I've got to hurry back to Centerville. Better go over all 
 of your field connections and see that there aren't any more in 
 that fix. And make the boy unclamp the heavy terminals and 
 clean the surfaces; they look dirty. Telephone me if you have 
 any more trouble." 
 
 Jones' final suggestion proved to be well advised, even if super- 
 fluous. Immediately after supper he was called to the telephone 
 to talk to the engineer. 
 
 "Hello; what's the row?" 
 
 "That 250-volt dynamo won't hold up its voltage," said the 
 engineer. "I've had to keep the boy at the rheostat to move it 
 up every time the load increases." 
 
 "E.M.F. drops when the load increases, does it?" 
 
 "Yes; and drops a great deal. We've passed the 'peak' of the 
 load all right, but the dynamo didn't take its share with the 
 rheostat all out." 
 
 "E.M.F. come up again when the load lightened?" 
 
 "Yes; the load is light now, and we have to hold her down with 
 the rheostat?" 
 
 "vSpark at the brushes under heavy load?" 
 
 "Yes, like the devil." 
 
 "I never saw the devil spark at the brushes. As soon as the 
 load falls to where the other dynamos can take it all, cut out your 
 bad-working machine and reverse its series field connections at 
 the terminal blocks. Then put it in circuit again and try it." 
 
Another Case of "Dead" Dynamo — Low Voltage. 
 
 41 
 
 In the course of two hours Jones was called up again. 
 "Works like a lamb, now," said the engineer. 
 "With the series field coils reversed?" asked Jones. 
 "Yes." 
 
 "Then your bo}^ must have swapped over the connections when 
 he cleaned the terminals to-day." 
 
 The engineer touched the shunt field terminals with the plugs. 
 
 "So that the series coils were connected backward and 
 weakened the field as the load increased ?" 
 "Yes." 
 
 Jones heard a mufifled imprecation in the receiver. 
 "That all?" he asked. 
 
 "Yes — no. What caused the sparking?" 
 "The weakness of the field. Good-night." 
 
CARELESS MOTORMEN — AN EQUALIZER TROUBLE. 
 
 Millville had just assumed the glory of an electric railway — a 
 ''belt line" which bounded the heart of the town and had an ex- 
 tension from the upper end of town through an outlying factory 
 district to the "fair grounds." 
 
 While the railway was owned by private capital an arrange- 
 ment had been made for current to be supplied from the town 
 power house presided over by our friend the engineer, and the 
 necessary generators and engines had been duly installed there 
 • — two direct-connected units of lOO kilowatts each. 
 
 The superintendent, electrician and engineer-in-chief of the 
 railway plant, according to Sam's homely judgment, was "a orn- 
 ery dum critter, so sweet on hisself he's 'bout to spile." This 
 official occasionally annoyed the engineer by ofhciousness during 
 the latter's absence. 
 
 On a gala day soon after the railway started up, when the travel 
 out toward the fair grounds was unusually heavy, the engineer 
 overheard the following colloquy upon returning from dinner: 
 
 "I ain't goin' to do it less'n the boss say so.'' 
 
 "But I tell you it's necessary, to keep the cars going." 
 
 "Can't he'p it; they'll hafter wriggle 'long best they kin till " 
 
 Bang! A circuit-breaker went out. 
 
 "There, now, don't you ' 
 
 "What's the trouble, Mr. Harvey?" asked the engineer, step- 
 ping into view. 
 
 "Well, you see," began the "ornery dum critter," somewhat 
 apologetically, "I only '.' 
 
 "He on')^ wanted me to tie up the circuit-breaker," broke in the 
 engineer's assistant bluntly, "an' I wouldn't." 
 
 "Mr. Harvey, do you use fuses on your cars?" asked the en- 
 o^ineer. 
 
Careless Motormen — An Equalizer Trouble. 
 
 43 
 
 'Why, of course, and- 
 
 "Do you make 'em useless by putting in iron or copper wire 
 instead of fuse-wire?" 
 
 "Cert'nly not; what do you think " 
 
 'Then why do you expect me to 'tie-in' a circuit-breaker?" 
 
 They'll hafter wriggle along as best they kin." Bang! 
 
 "Why, the d — d thing is going out all the time and stopping 
 my cars, and I can't afford to have 'em stopped every fifty feet." 
 
 "Then get rid of the trouble on the cars. I ain't going to tie- 
 in a circuit-breaker any more'n I'd tie down a safety valve on a 
 boiler." 
 
44 Central Station Experiences. 
 
 ''There ain't any trouble on the cars; it's the crowds we're 
 pulhng." 
 
 ''Well, I'll set the breaker on the fair-ground line a little stiffer; 
 that's the best I can do." 
 
 This incident naturally did not promote a David-and-Jonathan 
 friendship between the two chiefs. Nor did it enhance the en- 
 gineer's peace of mind, for he knew that the heavy travel could 
 not be the sole cause of the frequent "going out" of the circuit- 
 breaker on the fair-ground end. That night he dropped a note 
 to Jones, part of which ran thus : 
 
 "The circuit-breaker kept going out every few minutes, but it 
 was not the steady pulling that threw it. The ammeter needle 
 would nearly knock a hole in the side of the case each time the 
 circuit-breaker went out. What made the sudden jerking on the 
 line?" 
 
 Jones' answer was characteristic and gave the engineer an op- 
 portunity to deliver some sarcastic remarks to Mr. Harvey. 
 
 "Your d — d fool motormen were starting their cars on the 
 fourth or fifth controller notches instead of the first or second. 
 Call 'em down hard." 
 
 A few weeks later Jones dropped in on the engineer. 
 
 "Had any more trouble with circuit-breakers?" he asked. 
 
 The engineer grinned. "No," he said, "not since I gave 'em the 
 meat of your letter." 
 
 Jones chuckled. "Harvey's all right enough," he said, "but 
 he's new — dreadfully new. When he's seasoned he'll be a good 
 man. Everything else all right?" 
 
 "Yes, except we've been troubled a little in balancing the gen- 
 erators when both are in." 
 
 "What do they do?" 
 
 "They get out of balance as the load increases, and sometimes 
 it's so bad the boy has to stand by the rheostat until the heavy 
 load hour is over." 
 
 "Funny," said Jones. "T s'pose you've looked 'em over." 
 
 "Best I knew how," said the engineer. 
 
 "Feel of the field coils while they were running?" 
 
 "Yes, and tested 'em out when we shut down." 
 
 "Haven't changed any field connections?" 
 
 "Not a bolt." 
 
Careless Moiormen — An Equaliser Trouble. 
 
 45 
 
 "H'm," grunted Jones reflectively. "Funny. Let's take a look 
 again." 
 
 They examined the generators from top to bottom, but Jones 
 found nothing wrong. 
 
 "If it ain't in a generator it's bound to be in the equalizer," he 
 
 said after a few moments. 
 
 So they inspected the equalizer 
 leads from the generators to the 
 switchboard. Arriving at the 
 back of the board Jones lingered 
 the connections, gingerly, stand- 
 ing on an insulated stool (Fig. i). In a few moments he emitted 
 another grunt, this time of satisfaction. 
 
 "See here," he called out to the engineer, who left his inspection 
 of the neighboring generator panel and "saw here." 
 
 "Equalizer might almost as well have been in Africa." 
 
 "What's wrong?" 
 
 "Nuts jarred loose so that the end of the equalizer lead was 
 barely touching the nut next to it." 
 
 Sure enough, the connection was so loose that the wire terminal 
 had pulled away from the stud shoulder and was resting lightly 
 against the nut, as shown by Fig. 2. After 
 Jones had set up the nut and jam nut with a 
 wrench, the two men looked at each other, 
 Jones with his usual grin and the engineer 
 with a crestfallen air. 
 
 "Simple, wasn't it?" stepping out from 
 behind the board. 
 
 "Yes ;" said the engineer, following him, 
 "and if I hadn't so busy crowing over Har- 
 vey I'd have found it, I s'pose." 
 
 "Might not," said Jones. "Simple troubles 
 like that are harder to locate than big ones. 
 You see, I knew it had to be the equalizer 
 circuit somewhere because if the field coils were all right the only 
 thing that could keep 'em from balancing would be resistance in 
 the equalizing circuit." 
 
 "But the connection wasn't broken; I should think it would 
 balance the generators even if it was a poor contact." 
 
46 
 
 Central Station Experiences. 
 
 Jones resorted to his favorite pastime and drew Fig. 3. 
 
 "It did balance for a light load, but when the current went up 
 to a hundred amperes or so the 'drop' in the equalizer circuit at r 
 was so great that enough current wasn't forced across from a to 
 b or from & to a to balance the machines." 
 
 FIG. 3. 
 
 "'But some current must have gone over from one machine to 
 the other?" 
 
 "Yes," with a chuckle; "if it hadn't you'd have been sitting up 
 with the corpse of an armature — and maybe an engine." 
 
A SPARKING MOTOR ~ MOTOR WIRING. 
 
 Jones appeared one day in the doorway of a little den whiclr 
 the engineer had partitioned off for a ''testing room," and found 
 the engineer with knitted brows and a generally puzzled de- 
 meanor, regarding a little motor which was buzzing away at full 
 speed. 
 
 *'What are you playing?" he asked; ''special kind of solitaire?" 
 
 The engineer switched off the motor. "Yes," he said, with a 
 semi-smile, "I'm trying to find the key to the pure cussedness of 
 that motor." 
 
 "What does it do?" 
 
 "Runs like an angel down here and sparks like h — 1 up at the 
 coffee store. Commutator's been turned off twice in three 
 months." 
 
 "Thought angels always flew/' commented Jones. "Pictures 
 of 'em indicate that style of motion. What is there up at the 
 store to cause any difference in the motor?" 
 
 "Nothin'." 
 
 "Oh, yes; there is." 
 
 The engineer gazed at Jones' smiling visage in astonishment. 
 
 "How do you know?" 
 
 "If the motor works differently up there, the local conditions 
 must be different. Simply changing its location can't affect it." 
 
 "No, of course not. But there ain't a thing in sight to affect 
 it." 
 
 "Take a portable voltmeter and let's go up when the motor 
 goes." 
 
 Arriving at the coffee store, the motor was set up in its accus- 
 tomed place and when put to work it sparked viciously at the 
 brushes. 
 
48 
 
 Central Station Experiences. 
 
 Jones looked on in silence for a few moments and then began to 
 chuckle. 
 
 "I don't see anything to laugh at," complained the engineer. 
 
 "I'm not laughing. I'm only wondering how you expect that 
 motor to run smooth when you've got the field magnet almost 
 short-circuited." 
 
 "Where's any short-circuit?" demanded the engineer. 
 
 Jones pointed in silence to a big I-beam immediately over the 
 motor, which was set on a little platform hung from the I-beam. 
 
 "That doesn't touch the motor." 
 
 
 FIG. 1. 
 
 "It doesn't need to," said Jones. Don't you know you can't 
 insulate magnetism ?" 
 
 "I don't know just what you are driving at," said the engineer. 
 
 Jones cut off the motor. "No use to let it chew up that fresh 
 commutator surface," he said. "Now see here," and he drew 
 Fig. I. 
 
 "Those dotted lines represent magnetism leaking across from 
 your field magnet to the I-beam. The result is that your field is 
 weakened. 
 
 "So that the armature reaction causes sparking?" 
 
 "Exactly." 
 
A Sparking Motor — Motor Wiring. 
 
 49 
 
 "It will run above speed until the load becomes too great for 
 it to pull at the higher speed. Try it." 
 
 The motor was turned on. With no load it ran at a high rate 
 of speed. With two cofifee grinders connected up it slacked 
 down considerably and sparked fiercely at the brushes. 
 
 "Turn it around so the pulley will be in the same place, but the 
 motor will be out from under that I-beam/' suggested Jones. 
 
 ""Why doesn't it run faster then ?" 
 
 1 1 ''////////, / 
 
 '' I don't see anything to laugh at." 
 
 When this was done the motor ran smoothly and without a 
 spark, but the speed slacked greatly when the load was increased. 
 
 "Connect up the voltmeter and read it at no load and full load." 
 
 The engineer did so. 
 
 "No load 229 volts; full load 213," he reported. "Wires too 
 small ?" 
 
 Jones nodded. 
 
 "Better get a good wiring table or set of 'em," he said. "You'll 
 need all kinds and conditions of wiring before long." 
 
 "What size should these leads be?" asked the engineer. 
 
 "What size are they now?" 
 
50 
 
 Central Station Experiences. 
 
 "No. 10," after inspection. 
 
 "Then they should be either No. 7, or Nos. 6 and 8." 
 
 "What do you mean by Nos. 6 and 8?" 
 
 "One leg No. 6; the other No. 8. Here, take my motor wiring 
 table and use it until you get a wiring book," and he took from 
 his note-book a sheet containing the table here reproduced. 
 
 
 
 
 
 
 
 
 
 M( 
 
 )TOR WIRIN 
 
 G TABLE. 
 
 
 
 
 
 
 
 
 
 no Volts. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 220 Volte. 
 
 V. 8 
 
 
 Figures 
 
 at 
 
 top o( columns are Wire N 
 
 umbers, B & 
 
 S. gauge. 
 
 
 
 
 
 
 
 S c 
 
 1 1 
 
 
 Figures 
 
 in body of table are distances in feet 
 
 from main line to motor; t. 
 
 e, the actual lenirth of one Wire. 
 
 11 
 
 i < 
 
 
 The Table 
 
 s computed Tor a drop of 
 
 h% to 
 
 WW- 
 
 
 
 
 
 
 
 
 t -i 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 "s 5 
 
 ■2 2 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 3 2 
 
 ta t 
 
 < 
 
 2 
 
 -e&3 
 
 3 
 
 3&4 
 
 4 
 
 4&5 
 
 5 
 
 5&6 
 
 6 
 
 6&8 
 
 8 
 
 8&10 
 
 10 IC 
 
 &12 
 
 12 
 
 12&14 
 
 M 
 
 .1 
 
 
 
 ~ 
 
 
 
 
 
 
 
 
 
 
 784 
 
 638 
 
 490 
 
 400 
 
 290 
 
 5 
 
 
 
 
 
 "'\ 
 
 
 !!!! 
 
 
 
 
 
 922' 
 
 712 
 
 580 
 
 448 
 
 364 
 
 280 
 
 5J I 
 
 3 
 
 
 
 
 
 
 
 
 i!" 
 
 
 '.'.". 
 
 ! ! . ! 
 
 845 
 
 652 
 
 530 
 
 410 
 
 334 
 
 258, 
 
 6 
 
 (44 
 
 
 
 
 
 
 
 
 
 
 896 
 
 692* 
 
 563 
 
 434 
 
 354 ■ 
 
 274 
 
 223 
 
 172 
 
 9 
 
 ' . 
 
 
 
 
 
 
 
 '.!!! 
 
 
 990' 
 
 807 
 
 623 
 
 608 
 
 
 319 
 
 245 
 
 200 
 
 145 
 
 11 * 
 
 
 
 
 
 
 
 
 
 900 
 
 733 
 
 666 
 
 460 
 
 356 
 
 290 
 
 224 
 
 182 
 
 140 
 
 6 
 
 
 
 
 
 
 
 
 933 
 
 825 
 
 672 
 
 519 
 
 422 
 
 326 
 
 265 
 
 205 
 
 167 
 
 129 
 
 12 
 
 . Si 
 
 
 
 
 
 
 
 960 
 
 860 
 
 762 
 
 620 
 
 479 
 
 390 
 
 300 
 
 245 
 
 190 
 
 154 
 
 119 
 
 13 
 
 *i! 
 
 
 
 
 
 
 
 892 
 
 799 
 
 707 
 
 576 
 
 445 
 
 362 
 
 279 
 
 227 
 
 176 
 
 143 
 
 110 
 
 '^U 
 
 n 
 
 
 
 
 
 
 940' 
 
 832 
 
 746 
 
 660 
 
 536 
 
 414 
 
 338 
 
 260 
 
 212 
 
 164 
 
 132 
 
 102 
 
 15('* 
 
 8 
 
 
 
 
 
 984 
 
 882 
 
 780 
 
 699 
 
 619 
 
 503 
 
 389 
 
 316 
 
 244 
 
 199 
 
 154 
 
 125 
 
 96 
 
 16 V 
 
 9 
 
 
 
 
 988' 
 
 875 
 
 784 
 
 694 
 
 622 
 
 550 
 
 448 
 
 346 
 
 280 
 
 217 
 
 177 
 
 137 
 
 110 
 
 86 
 
 18 5 4 
 
 1 10 
 
 
 '...'. ' 
 
 93' 
 
 890 
 
 787 
 
 705 
 
 62+ 
 
 559 
 
 495 
 
 403 
 
 312 
 
 254 
 
 1%6 
 
 159 
 
 123 
 
 100 
 
 77 
 
 .20 
 
 ) 
 
 - 11 
 
 
 
 m 
 
 809 
 
 716 
 
 640 
 
 667 
 
 503 
 
 450 
 
 
 283 
 
 230 
 
 178 
 
 145 
 
 112 
 
 90 
 
 70 
 
 22 
 
 5 
 
 12 
 
 
 935 
 
 27 
 
 740 
 
 656 
 
 588 
 
 520 
 
 466- 
 
 412 
 
 336 
 
 259 
 
 210 
 
 163 
 
 132 
 
 102 
 
 83 
 
 64 
 
 24 
 
 
 Hi 
 
 863 
 
 774 
 
 )85 
 
 614 
 
 643 
 
 487 
 
 430 
 
 385 
 
 340 
 
 1^ 
 
 214 
 
 174 
 
 135 
 
 09 
 
 85 
 
 69 
 
 53 
 
 29 
 
 
 H 15 
 
 834 
 
 748 ( 
 
 )62 
 
 593 
 
 526 
 
 470 
 
 416 
 
 373 
 
 330 
 
 207 
 
 169 
 
 ISO 
 
 06 
 
 82 
 
 66 
 
 50 
 
 30 
 
 
 
 782 
 
 700 
 
 20 
 
 556 
 
 492 
 
 440 
 
 
 349 
 
 309 
 
 250 
 
 194 
 
 158 
 
 122 
 
 99 
 
 77 
 
 62 
 
 43 
 
 32 
 
 n 
 
 n 
 
 736 
 
 660 £ 
 
 84 
 
 524 
 
 463 
 
 415 
 
 367 
 
 329 
 
 290 
 
 237 
 
 183 
 
 149 
 
 115 
 
 93 
 
 72 
 
 58 
 
 45 
 
 34 
 36 
 
 
 18 
 
 695 
 
 623 
 
 >60 
 
 494 
 
 437 
 
 392 
 
 347 
 
 310 
 
 275 
 
 224 
 
 173 
 
 140 
 
 108 
 
 88 
 
 68 
 
 55 
 
 43 
 
 
 2 \ 19 
 
 659 
 
 590 £ 
 
 22 
 
 468 
 
 414 
 
 370 
 
 328 
 
 294 
 
 260 
 
 212 
 
 164 
 
 133 
 
 103 
 
 84 
 
 65 
 
 62 
 
 40 
 
 38 
 
 
 20 
 
 626 
 
 560 i 
 
 96 
 
 445 
 
 393 
 
 
 312 
 
 279 
 
 247 
 
 200 
 
 156 
 
 127 
 
 98 
 
 79 
 
 60 
 
 50 
 
 38 
 
 40 
 
 10 
 
 .21 
 
 596 
 
 628 1 
 
 72 
 
 423 
 
 375 
 
 335 
 
 297 
 
 265 
 
 235 
 
 190 
 
 148 
 
 120 
 
 93 
 
 75 
 
 58 
 
 
 
 42 
 
 
 669 
 
 510 4 
 
 152 
 
 404 
 
 358 
 
 320 
 
 283 
 
 254 
 
 225 
 
 183 
 
 142 
 
 115 
 
 89 
 
 72 
 
 56 
 
 
 
 44 
 
 
 
 fHS 
 
 480 
 
 432 
 
 !82 
 
 342 
 
 303 
 
 270 
 
 240 
 
 215 
 
 190 
 
 155 
 
 120 
 
 98 
 
 75 
 
 60 
 
 48 
 
 
 
 
 
 27 
 
 463 
 
 415 
 
 68 
 
 330 
 
 292 
 
 260 
 
 230 
 
 209 
 
 187 
 
 160 
 
 115 
 
 
 72 
 
 59 
 
 46 
 
 
 
 66 
 
 68^-15 
 
 3 
 
 28 
 
 447 
 
 400 : 
 
 154 
 
 318 
 
 282 
 
 252 
 
 223 
 
 199 
 
 177 
 
 144 
 
 110 
 
 90 
 
 70 
 
 57 
 
 44 
 
 
 
 
 ?. 
 
 432 
 
 387 
 
 142 
 
 307 
 
 272 
 
 243 
 
 215 
 
 192 
 
 170 
 
 138 
 
 107 
 
 87 
 
 67 
 
 54 
 
 42 
 
 
 
 
 L30 
 
 417 
 
 374 S 
 
 130 
 
 296 
 
 262 
 
 236 
 
 208 
 
 186 
 
 165 
 
 134 
 
 103 
 
 84 
 
 65 
 
 
 
 
 
 
 r38 
 
 329 
 
 295 5 
 
 60 
 
 234 
 
 207 
 
 185 
 
 164 
 
 147 
 
 130 
 
 106 
 
 82 
 
 06 
 
 61 
 
 
 
 
 
 76 
 
 80 20 
 84 
 
 
 *2 
 
 313 
 
 280 -2 
 
 18 
 
 222 
 
 196 
 
 176 
 
 156 
 
 139 
 
 123 
 
 100 
 
 78 
 
 63 
 
 49 
 
 
 
 
 
 
 5 
 
 42 
 
 92 
 
 264 5 
 
 36 
 
 210 
 
 187 
 
 167 
 
 148 
 
 132 
 
 117 
 
 95 
 
 74 
 
 
 
 
 
 
 
 
 44 
 
 284 
 
 255 5 
 
 •26 
 
 202 
 
 179 
 
 160 
 
 140 
 
 127 
 
 112 
 
 91 
 
 71 
 
 
 
 
 
 
 
 
 
 46 
 
 272 
 
 243 : 
 
 15 
 
 193 
 
 170 
 
 153 
 
 135 
 
 120 
 
 107 
 
 87 
 
 67 
 
 
 
 
 
 
 .... 
 
 
 
 (-56 
 
 223 
 
 200 
 
 77 
 
 159 
 
 140 
 
 126 
 
 110 
 
 99 
 
 88 
 
 72 
 
 65 
 
 
 .... 
 
 
 
 
 
 
 
 58 
 
 216 
 
 193 
 
 70 
 
 153 
 
 136 
 
 120 
 
 107 
 
 96 
 
 85 
 
 
 
 
 .... 
 
 
 
 
 
 
 'i 
 
 ^ 
 
 208 
 
 187 
 
 65 
 
 148 
 
 130 
 
 117 
 
 104 
 
 93 
 
 82 
 
 
 
 
 
 
 
 
 
 
 
 62 
 
 202 
 
 180 
 
 60 
 
 143 
 
 127 
 
 113 
 
 100 
 
 90 
 
 80 
 
 
 
 
 
 
 
 
 
 
 
 64 
 
 195 
 
 175 
 
 55 
 
 139 
 
 123 
 
 110 
 
 
 87 
 
 77 
 
 
 
 
 
 
 .... 
 
 
 
 
 
 72 
 
 174 
 
 156 1 
 
 38 
 
 123 
 
 109 
 
 98 
 
 87 
 
 77 
 
 68 
 
 
 
 
 
 
 
 
 
 
 10 
 
 74 
 
 76 
 80 
 
 169 
 164 
 156 
 
 151 1 
 
 147 
 
 140 
 
 34 
 30 
 24 
 
 120 
 117 
 111 
 
 106 
 103 
 
 98 
 
 95 
 92 
 88 
 
 84 
 82 
 78 
 
 
 
 
 
 
 
 
 
 . .. 
 
 
 
 Wire 
 
 Nos. 
 
 2 
 
 2&3 
 
 r 
 
 3&4 
 
 4 
 
 4&5 
 
 5 
 
 5&6 
 
 6 
 
 6&8 
 
 8 ' 
 
 8&10 
 
 10 10 
 
 &12 
 
 12 
 
 2 &14 
 
 14 
 
 
 Safe 
 Current 
 
 130 
 
 1 1 
 
 10 
 
 ,. 
 
 92 
 
 77 
 
 77 
 
 65 
 
 65 
 
 46 
 
 46 
 
 32 
 
 32 
 
 23 
 
 23 
 
 16 
 
 16 
 
 
 The engineer thanked him, and they started back to the station. 
 
 "Why did you say awhile ago that I'd need all sorts of wiring 
 soon?" asked the engineer. 
 
 "Because you will. The town has about decided to put in an 
 alternator and to lease the old water-power and mill site up the 
 river so's to furnish light and power to the shops and factories 
 out at the west end, and you're going to do a lot of wiring calcu- 
 lations." 
 
A Sparking Motor — Motor Wiring. 51 
 
 "But I don't know how exactly." 
 
 "You can learn." 
 
 Reaching the station the engineer took out Jones' wiring table 
 and spread it on the desk. 
 
 "Why are there several numbers of amperes for each size of 
 motor?" he asked. 
 
 "Because different motors show different efficiencies, and there- 
 fore require different amounts of current." 
 
 "That's so. According to the table this motor will need Nos. 6 
 and 8 wire, just as you guessed." 
 
 "I didn't guess; I knew." 
 
 "How could you know?" 
 
 "With No. 10 wire your drop is 16 volts, isn't it?" 
 
 "Yes." 
 
 "Well, seven or eight volts is as much as you ought to have on 
 a 220 or 230 volt circuit. And in order to cut your drop down 
 from sixteen volts to about eight, your wire must be about twice 
 the size it is." 
 
 -Yes, but " 
 
 "Wait. No. 7 wire is roughly twice the size of No. 10, but No. 
 7 wire is not generally kept in stock. As No. 7 is about half way 
 between No. 6 and No. 8, making half of your circuit of No. 6 
 and the other half of No. 8 will give practically the same result." 
 
 "I don't exactly see that." 
 
 "No. 6 wire has an area of 26,250 circular mils," referring to 
 his notebook, "and No. 8 has 16,510 circular mils. Now if half 
 of the circuit is of one size and half of the other size, the average 
 area throughout the circuit will be the plain average of these two 
 areas. What is the average or mean of 26,250 and 16,510?" 
 
 The engineer wrote: 26,250 
 
 16,510 
 
 2)42,760 
 
 21,380 
 
 "Twenty-one thousand, three hundred and eighty circular 
 mils," he said. 
 
 "All right. Now No. 7 wire has an area of 20,817 circular mils, 
 so that Nos. 6 and 8 used together give slightly less drop than 
 No. 7 would." 
 
52 Central Station Experiences. 
 
 "1 see. And Nos. lo and 12 can be used instead of No. 11; 
 Nos. 8 and 10 instead of No. 9, and so on?" 
 
 ''Exactly. Thus you get a greater number of available wire 
 areas or resistances without carrying any more sizes in stock." 
 
 The engineer pored over the wiring table for several minutes. 
 
 "Suppose I wanted to wire a 5-horse motor and didn't know 
 how many amperes it would take?" he suggested. 
 
 "Assume the middle figure, in such a case. The wiring will be 
 near enough for all practical purposes." 
 
 "Forty-two amperes for a iio-volt five-horse, and twenty-two 
 amperes for a 220-volt five-horse?" he asked. 
 
 "Yes." 
 
 "How can you use the table for some other percentage of 
 drop?" 
 
 "Multiply the actual amperes by the drop you want, divide by 
 3.6, and use the result as if it were the amperes your motor de- 
 manded. But I wouldn't bother with any other drop. Three and 
 six-tenths per cent is a good all round drop and will fit any case 
 within reason. Get your wiring book — but get a good one that 
 contains something more than kid lessons on Ohm's law — and 
 you will have tables for all practical drops. Be sure it includes 
 alternating-current wiring." 
 
 "Is that any different ?" 
 
 "Considerably. Direct current wiring tables are no earthly 
 good for alternating-current circuits." 
 
SOME RAILWAY KINKS. 
 
 Since the circuit-breaker episode Mr. Harvey and the engineer 
 had become better acquainted, and each had discovered, as usually 
 befalls, that the other had "lots more sense" than he had sup- 
 posed. Moreover, Harvey's '"'newness" had worn off greatly, and 
 he had come down to an appreciation of his own limitations. If 
 
 "The old man'd raise caln." 
 
 I may be permitted to digress a little from the historical to an 
 advisory line, I would like to urge upon young engineers the 
 fact that an accurate weighing of one's own ability, coupled with 
 confidence and a determination to improve, results in success 
 ninety-nine times in a hundred. 
 
54 Central Station Experiences. 
 
 Harvey was rapidly attaining this frame of mind ; hence he and 
 the engineer found mutual benefit in frequent consultations, and 
 appeals to Jones' superior experience were not so often neces- 
 sitated as they had been previously. Thus it happened that 
 Harvey called on the engineer one day nearly a year after the 
 circuit-breaker occasion, for ''consultation." 
 
 "It's mighty nigh time for that old fair ag'in," he said, "and 
 we'll have to do something to provide for the crowds." 
 
 "Got no extra cars?" queried the engineer. 
 
 "Oh, yes; plenty o' cars. But the feeders out there ain't 
 calc'lated to keep up the pressure with such heavy loads." 
 
 "We might run some temporary feeders — hang 'em up from 
 the cross-arms by loops from porcelain knobs," suggested the 
 engineer. 
 
 "Lot o' work, and the wire's bound to be more or less dam- 
 aged." 
 
 "Yes. Really, the feeders ought to be reinforced permanently 
 so's we could carry extra loads." 
 
 "The old man 'd raise Cain if I asked him to put in that much 
 extra wire just for the fall fair." 
 
 "Figured out what 'twould take?" 
 
 "Roughly. We've got three feeders out there now; a mile o' 
 No. 2, two miles o' No. oo and three miles o' No. oooo wire. The 
 drop with two cars, one going out and one coming in, is about 
 60 volts, so we'd need to put in two more sets o' feeders to handle 
 six cars at the same drop." 
 
 "That's so, or nearly so. You'd need two more No. 0000 feed- 
 ers out to the far end; a No. 0000 near the middle and a No. 00 
 out to the near end of the branch line. Eight miles of No. 0000 
 and a mile of No. 00. Whew!" 
 
 Harvey nodded gloomily. 
 
 "That's what I figured out, and I might's well ask the old man 
 for a pair o' gold wings as all that wire." 
 
 Suddenly the engineer jumped up and said emphatically: 
 
 "Well I'll be d d." 
 
 "That won't help the cars any," said Harvey, but he brightened 
 up under the influence of the engineer's jubilant countenance. 
 
 "What's struck you?" 
 
 "Booster," sententiously. 
 
Some Railway Kinks. 
 
 55 
 
 *'You did seem to get a pretty good lift out o' that chair. 
 Where's any booster?" 
 
 The engineer took Harvey by the coat lapel, and leading him 
 out into the dynamo room, pointed dramatically towards the 
 dynamos and said: ''There!" 
 
 'Ts it wheels you've got, or snakes?" 
 
 The engineer laughed and went back in his den. 
 
 *'See here," he said, drawing a diagram like Fig. i and remark- 
 ing, 'T'm getting into Jones' habits." 
 
 VwS- -vr«v^ 
 
 -^K^aAr 
 
 FIG. 2. 
 
 Harvey looked on in silence. 
 
 ''All we need to do is to disconnect your three fair-ground feed- 
 ers from the bus-bars and put one of my 500-light dynamos in 
 series with all three of them, hke that." 
 
 "Goin' to leave her self-exciting?" 
 
 "Yes; why not?" 
 
 "Lemme draw a little," said Harvey, with a smile. And he 
 drew Fig. 2. 
 
 "I was just wondering about the current in that field circuit," 
 
56 
 
 Central Station Experiences. 
 
 he said. ''The current must go like the arrows for the dynamo to 
 work; now won't the generators force current backward through 
 the booster dynamo's field?" 
 
 The engineer hesitated. 
 
 'T don't think so," he said. ''You see, the 
 E.M.F. that forces current through the dynamo 
 field is furnished by its own armature." 
 
 "Yes ; but the railroad generator is furnishing 
 the most of the E.M.F., and the current going 
 out on the line must divide when it comes to the 
 dynamo, part'll go through the armature and be 
 boosted, and a little will go through the field " 
 
 "And be kicked back. No ; I don't believe any 
 of the feeder current will get through the field 
 circuit of the boosting dynamo." 
 
 "Well, well, well; what's the game?" broke 
 in a familiar voice, and Jones' chubby visage 
 seemed to fill up the entire doorway. 
 
 "You always turn up at the right minute," 
 said the engineer 
 
 "Born that way," broke in Jones. "What's up ?" 
 
 The case was soon laid before him, and his usually sunny coun- 
 tenance clouded slightly. 
 
 "T'll be ashamed of you fellows if you don't use your brains 
 more. Why should you be in doubt about it ?" 
 
 "Well, we — that is — of course — " stuttered Harvey. 
 
 "Suppose," said Jones, drawing Fig. 3, "you had this condition. 
 What would be the joint resistance of the two coils in parallel ?" 
 
 The engineer scribbled hurriedly, with the result below: 
 
 -I 
 
 FIG. 3. 
 
 \\ 100 ^ * 100 
 
 10. t oy^ fci 
 
 lo«) tcoooC. o<|£j 
 
 "Ninety-nine thousandths of an ohm," he announced. 
 
So))ie Railway Kinks. 57 
 
 "Then what's the drop if the current is a hundred and one 
 amperes ?" 
 
 'Ten volts," after scratching for a few seconds. 
 
 "Then if the left-hand coil became an armature giving one 
 hundred to one hundred and ten volts^ do you think the ten volts 
 originally at the terminals of the field coils could overcome it 
 and force current through backwards?" 
 
 "I never said it would," asserted the engineer; "but I wasn't 
 absolutely sure about it," he confessed. 
 
 "You win have to be careful, though," said Jones, "in using 
 that arrangement. The feeders must be disconnected until the 
 dynamo has picked up and reached its full field strength." 
 
 "What difference would it make?" 
 
 ''Reason it out and see." 
 
 The engineer and Harvey studied Fig. 2 a few moments. 
 
 "If it was put in circuit not running," said Harvey, "the field 
 would be excited backwards and when the dynamo started it 
 would oppose the feeder current instead of helping it." 
 
 "Exactly. That is one reason why a series-wound booster is 
 preferable. The principal reason, however, is that the more cur- 
 rent there is the more voltage the booster adds, so that the E.M.F. 
 at the far end may be kept absolutely constant no matter what the 
 load is." 
 
 "There's something else I'd like to ask you," said Harvey. 
 "I've got a car that runs at the same speed on the last controller 
 notch that it does on the one next to it. Why is that?" 
 
 "What kind of a controller?" 
 
 "K2." 
 
 "Nothing seems wrong anywhere else?" 
 
 "No. The controller contacts are all right, and there ain't a 
 sign o' trouble anywhere." 
 
 "H'm. Which controller notch is the speed correct for?" 
 
 "Dunno." 
 
 "Then you might profitably spend a while finding out. If the 
 car runs at full speed on the eighth notch that notch has be- 
 come the same as the ninth, by some accidental contact. If the 
 car never gets beyond the eighth notch speed, then the ninth 
 notch is 'killed' by something wrong." 
 
 "What could be the trouble in each case?" 
 
58 Central Station Experiences. 
 
 "If your car runs slow on the ninth notch, the shunt resistances 
 are not connected. If it runs at full speed on the eighth notch, 
 then the shunt resistances are thrown in at that notch instead of 
 the ninth. The trouble is almost certainly in the shunt resistance 
 circuity no matter whether the result is eighth-notch speed at both 
 notches, or ninth-notch speed at both. It's more likely to be dis- 
 connected shunt resistances than accidental contact between con- 
 troller fingers. Test out your shunt resistance circuits and you'll 
 find it." 
 
READING A RECORDING WATTMETER. 
 
 "Harvey, do yon know anything about meters?" asked the en- 
 gineer, plaintively, as he watched the dignified rotation of a 
 Thomson recording watt-hour meter. 
 
 "Divil a bit," replied Harvey, who boasted a Celtic ancestor 
 and occasionally took this method of manifesting his pride 
 therein. "What's the trouble?" 
 
 The engineer rubbed his chin abstractedly and gazed at the 
 meter again. 
 
 "It seems to run all right up here," he explained, "but it don't 
 register anywhere near right at Briggs' store." 
 
 "How d' you know 'tain't right?" 
 
 "Weh, Briggs' bill was so derned triflin' last month and the 
 month before, I knew the' must be a screw loose somewhere. So 
 I had Jimmie take ammeter readin's for an hour yesterday, 'n' 
 the meter registered short." 
 
 "What kind o' load has Briggs got?" 
 
 "What's that got to do with it?" 
 
 "I dunno," responded Harvey, frankly. "Over to Durham, 
 where I was before I come here, they had a lot o' these on, an' I 
 remember Perkins told the meter man there 't the' wa'n't no use 
 'xpectin' a meter to talk; 't 'twa'nt intended for that kind o' load." 
 
 "What kind of a load did he mean?" asked the engineer^ 
 anxiously. 
 
 "Dunno that," again acknowledged Harvey, "but it's evident 
 that the's some kind of a load the fool things ain't good for." 
 
 "It seemed to run all right before we put in that other motor," 
 said the engineer. 
 
 "What other motor?" 
 
 "The little freight elevator motor." 
 
 Harvey's face lightened. 
 
6o Central Station Experiences. 
 
 "Then that must be the kind o' load Perkins meant," he ex- 
 claimed. 
 
 The engineer shook his head dubiously and turned off the cur- 
 rent from the meter under discussion. 
 
 "Jones didn't say anything about it when he brought the first 
 meters here," he said. 
 
 "Probably didn't think of it. You didn't have any elevator 
 motors running then, did you ?" 
 
 "N— no." 
 
 " 'Spose we try the meter on the main load, with the elevator 
 motor tapped in between the entrance and the meter," suggested 
 Harvey. 
 
 "That's good," agreed the engineer, and the test was made, 
 Jimmie, the general utihty boy, being delegated to take ampere 
 readings every five minutes for an hour. The results checked 
 nearly enough to show that, allowing for the possible division of 
 Jimmie's attention between the ammeter and a blood-and-thunder 
 novel, the recording meter was accurate. 
 
 The engineer looked at Harvey and Harvey grinned tri- 
 umphantly. 
 
 "That's it," he said. 
 
 "Evidently; but what'll I do about the elevator motor?" 
 
 "Got a recording ammeter?" 
 
 "Yes; there's three on the station switchboard." 
 
 "Borrow one of 'em and put it in the elevator motor circuit for 
 a week and make 'em a flat rate based on what the ammeter 
 charts show. Put another wattmeter in and keep this one just as 
 it is to show Jones." 
 
 This course was pursued, after a lively interview with Briggs, 
 who was crusty and difBcult to convince. 
 
 Shortly thereafter the engineer related the experience to Jones. 
 
 "Now, why won't the recording meter register elevator motor 
 current as well as any other kind?" he asked. 
 
 "Do you know what inertia is ?" was Jones' counter-question. 
 
 "Of course." 
 
 "Well, then you know that the armature of that meter possesses 
 the quality called inertia, which tends to prevent any change in 
 speed." 
 
 "Yes, but " 
 
Reading a Recording Wattmeter. 
 
 6i 
 
 "Hold on. You also know that the speed of the armature is 
 almost precisely proportionate to the power of the circuit?" 
 
 **Yes; that's why " 
 
 "Don't get excited. Now, suppose your circuit has, say, 2 
 horse power passing, and the motor makes, say, 10 revolutions a 
 minute. Then imagine that your elevator motor is thrown on and 
 the power changes instantaneously to 10 horse power; do you 
 suppose the meter armature can change its rate from 10 to 50 
 revolutions a minute instantaneously T' 
 
 "N — no, of course not, but " 
 
 "All right. Now imagine that the power drops immediately to 
 4 horse power, after that spurt up to 10. Don't you see that the 
 meter can't possibly shift its rate of speed rapidly enough to 
 register all the changes accurately?" 
 
 '*Yes^ that's clear enough, but the spurts don't last long enough 
 to make any great difference." 
 
 "Not a tremendous difference, perhaps, but with a motor con- 
 stantly starting and stopping, the difference will be fairly big. 
 How much discrepancy did there seem to be?" 
 
 "Not very much the first month, but simply out o' sight the 
 second month." 
 
 "Then your boy read the meter wrong. Let's see the record 
 book." 
 
 The book was found to contain the following entries: — 
 
 X 
 
 CMrwe^ 
 
 db. 
 
 "^^rc 
 
 ;b. 2. 
 
 CotoWr 
 
 /o 
 
 
 "S^ove/ywio^^f* 
 
 \o 
 
 
 T/yfo^o 
 
 33e<LevAVyc-c 
 
 /z. 
 
 
 ?^?./ 
 
 "H'm," grunted Jones. "Where's the boy?" 
 
 Jimmie was summoned, and after some delay came running in 
 with a suspicious show of zealous haste. 
 
 "Jimmie," said Jones, in his most confidential, persuasive tone; 
 "Jimmie, how did you get at the reading of Briggs' meter this 
 month ?" 
 
 Jimmie turned as many colors as the possibilities of nature 
 
62 
 
 Central Station Experiences. 
 
 allow; stood on one foot, then on the other; looked over Jones' 
 head, then at the hat he was nervously twisting between his hands, 
 but was apparently dumb. 
 
 "Guessed at it, didn't you, Jimmie?" asked Jones in such an 
 unmistakably friendly tone that Jimmie thawed and broke down. 
 
 '*Y — y — yas^ sir," he stammered, digging his grimy knuckles 
 into his eyes to keep back the tears. 
 
 ''Now, don't cry, Jimmie," said Jones. ''I was a kid once and 
 learned the same sort of lesson you're learning now. Hereafter, 
 though, when you're not sure of a thing don't be afraid to say so, 
 or else find out what's correct before you report on it." 
 
 ""I did — didn't g — guess at o o only one figger," sobbed 
 
 Jimmie in an effort at partial justification. 
 
 "Which one?" 
 
 "The f — fust one. 'Tothers is r — right." 
 
 "All right. Now skip, and stop crying," which Jimmie did 
 with alacritv. 
 
 o 
 
 1000000 100000 
 
 ol 
 
 THOMSON RECORD(/Vq 
 
 WATT METER 
 10000000 GENERAL ELECTRIC CO. looo 
 
 r~\ WATT HRS. MULTIPLY BY 2, WATT HRS. (^ 
 V - ^ 
 
 FIG. 1. 
 
 "Makes me chicken-hearted to see a kid cry," said Jones, sheep- 
 ishly. "Got the Briggs meter out of service?" he asked. 
 
 The engineer brought it. 
 
 "Don't blame Jimmie very much for guessing," said Jones, 
 pointing to the dials, which stood as shown by Fig. i. "Can you 
 read *em?" 
 
 Harvey and the engineer looked at the dials and said in one 
 voice : 
 
 "Nine, two, eight, zero." 
 
 "Precisely not,'' said Jones with a grin. 
 
 Harvey and the engineer stared at him and then at the dials. 
 
 "What does it register?" asked the engineer. 
 
 ■"Nine, nine, two, eight, zero." 
 
Reading a Recording Wattmeter. 
 
 63 
 
 *'Where's the first nine?" 
 
 "Begin at the right-hand dial and you'll see. That's zero; next 
 one's not quite eight, but it must be eight because the first one is 
 at zero. Next one's not quite three, so two is right. Next one is 
 at nine, and the last one seems to be at zero, but it can't reach 
 zero accurately until the one on its right does. Therefore it must 
 be considered not quite up to zero, making the reading 9,928,000. 
 When it does reach zero, the last dial can be read 10, the one be- 
 ing prefixed because the hand will have made one revolution." 
 
 ''Oh! But where did Jimmie get the first 8?" 
 
 Jimmie stood on one foot, then on the other. 
 
 '"He read the meter 927,500, and knew that must be wrong, so 
 he prefixed a figure one unit larger than last month's register. 
 Quite a natural error." 
 
 "That's so," assented the engineer. "But even the corrected 
 reading is smaller than the average rate shown by the recording 
 ammeter." 
 
 "Yes, because that is more sensitive, naturally enough." 
 
 "Well, is there no way to make these meters record the sudden 
 changes in the elevator motor load?" 
 
64 
 
 Central Station Experiences. 
 
 "Not accurately. It will be sufficient to allow two per cent 
 extra for them, though. The meter will average up to within 
 that." 
 
 Jones rose to go. 
 
 "Hold on a minute; there are some other things," cried the 
 engineer. "Why didn't they make these meters to read direct in- 
 stead of multiplying the reading by 2 ?" 
 
 "Because the speed would be twice as high, and the inertia of 
 the armature would interfere with the accuracy four times as 
 much as it does now." 
 
 "Oh. Well, why do some of the motors creep when there's no 
 load on?" 
 
 "Because they are too perfect," said Jones, laughing. "In 
 other words, they move too easily." 
 
 "But what is there to make 'em mov^?" 
 
 fA 
 
 r-n 
 
 ^^ 
 
 ■ 
 
 r 
 
 RESISTANCE 
 
 FIG. 2. 
 
 Jones took out his note-book and turned to a diagram like 
 Fig. 2. 
 
 "If you trace these connections," he said, "you will find that 
 with no lamps on, current will flow from the + li^^ wire through 
 the series field coils between A and B, then through the shunt 
 coil and armature to C, and out to the negative line wire. Al- 
 though it is almost infinitesimal, this current may cause a meter 
 to creep if it is unusually free running." 
 
 "Can't it be remedied ?" 
 
 "Yes; easily. Transfer the shunt field connection from B to 
 A, and the meter probably won't creep." 
 
o ►- jc 
 
 FIG. 3.-ELECTRIC POWER PRICE CHART 
 
66 Central Station Experiences. 
 
 "Why wasn't it fixed that way?" 
 
 ''Because it is intended to measure only the work done beyond 
 it. As it stands it does this. If you change the shunt field con- 
 nection over to A, the meter will register the work done in its own 
 series coils in addition to the customer's load. But the increase is 
 unimportant." 
 
 As Jones closed his note-book a sheet of paper fluttered to the 
 floor. 
 
 ''Hello," he said, as he picked it up and opened it. "I brought 
 that for you and forgot to give it to you." 
 
 It was the price-chart shown by Fig. 3. This chart is divided 
 into two parts by the white space cutting diagonally across it. 
 Above this dividing line the figures up the left-hand margin must 
 be used; below it, the figures along the right-hand margin. To 
 use the chart, find the number of kilowatt-hours on the top or 
 bottom line of the diagram ; follow vertically along that line until 
 the diagonal line representing the price per kilowatt-hour is 
 reached; then follow the horizontal line there found over to the 
 margin. At the end of it will be found the amount of the bill. 
 
BRAKING A CAR WITH ITS MOTORS. 
 
 'Say, I've got an idea," exclaimed Harvey one afternoon, as he 
 and the engineer sat basking in the sunshine of a prematurely 
 springlike day. 
 
 "You're in dead luck," observed the engineer. "It don't hurt 
 you, does it?" 
 
 "No," replied Harvey, good-humoredly; "it's this way. See 
 that car comin' down the West End hill ?" 
 
 The engineer looked down the river and over toward a hill- 
 side around which a trolley car was slowly creeping, and nodded. 
 
 "That infernal hill is more worry 'n all the rest o' the blamed 
 road put together, and I'm goin' to " 
 
 "Have it leveled?" suggested the engineer, chaffingly. 
 
 "Not quite; but I'm goin' to fix the cars so's they'll come down 
 there without workin' the men to death and keepin' 'em uneasy 
 all the way down. I'll fix 'em so they can't get beyond a safe 
 speed, even with the brakes entirely off," announced Harvey tri- 
 umphantly. "What d'you think o' that for a scheme?" 
 
 The engineer straightened up and regarded the speaker with 
 renewed interest, and an interrogatory expression of countenance. 
 
 "It's bang up if you do it," he replied, "but it ain't done yet." 
 
 "No, but it's a cinch, though," asserted Harvey confidently. 
 
 "Trailin' anchor?" suggested the engineer. 
 
 "Nope. Perfectly automatic brakin' scheme." 
 
 "Fiddle," said the engineer, contemptuously. "Automatics 
 ain't any good for street car work. You have to have a whole 
 machine shop aboard and keep two extra men on a car to keep 
 the stuff a-goin'." 
 
 "Just you hold on " 
 
 "More'n your blessed brake'll do!" 
 
 "See here a minute," argued Harvey; "if I short-circuit the car 
 
68 
 
 Central Station Experiences. 
 
 motors through a low resistance, hke this," drawing Fig, i, "why 
 won't they generate current and hold the car back?" 
 
 The engineer looked at the diagram thoughtfully. 
 
 "That's been tried, I think," he said, " and it wasn't a success." 
 
 mmmwamnnkt 
 
 QJ- 
 
 FIG. 1. 
 
 Harvey scratched his head and looked skeptical. 
 
 "I don't see any reason why it shouldn't work," he said. "It's 
 only a question of gettin' the resistance right so's not to brake the 
 car too heavy or run any risk o' burnin' out the motors." 
 
 "Looks that way," admitted the engineer, "but I'm sure it's 
 been tried 'n' failed." 
 
 "Well, I'm goin' to give it another chance to fail," asserted 
 Harvey with a grin. "It won't cost much to rig a switch on the 
 dash to make the connection across from outside to outside o' 
 the motors through a resistance." 
 
 The engineer studied Harvey's rough sketch for several min- 
 utes in silence. At length he asked: 
 
 "How about the connections between the motors?" 
 
 "Why, the controller makes them." 
 
 "Not when it's in the *ofif' position." 
 
 ti-bujiJUH^ — a] 
 
 FIG. 2. 
 
 "vvvwvvwvvvvvv-- 
 
 ^yj\j\^^Mm^f^--^^ — umm Q^yuuuib 
 
 Harvey looked puzzled for a moment. Then his face lighted 
 up and he let the front legs of his chair down with a bang and 
 abandoned its comfort to pace up and down excitedly. 
 
 "Gee whillikens!" he exclaimed. "That's a dandy scheme!" 
 
Braking a Car ivith Its Motors. 69 
 
 "What is?" 
 
 "This," and he hastily scrawled the diagram shown by Fig. 2. 
 "'If I put in a double-throw switch this way to cut the controller 
 loose from the trolley 'n' connect it to the end of a resistance coil 
 then the brakin' effect o' the motors can be regulated with the 
 controller itself. Ain't that great?" 
 
 "It looks all right," agreed the engineer after looking over the 
 diagram carefully, "but I wouldn't trust it 'til I'd tried it and 
 made sure." 
 
 "Course not," said Harvey. "How much resistance d'you 
 think it'll take in series with the motors?" 
 
 "I don't believe you'll need any extra resistance besides the 
 coils already on the car," said the engineer. "I guess we can get 
 a rough idea of it with a little figurin'. About how much does a 
 car weigh ?" 
 
 "Close to five thousand pounds." 
 
 "And with fifteen passengers and the two men the whole thing'U 
 foot up about eight thousand pounds, won't it?" 
 
 Harvey nodded assent. 
 
 "What's that grade over there; 'bout ten per cent?" 
 
 "Nine, most of the way; the balance of it's less." 
 
 "Then if the car comes down at four miles an hour, how many 
 feet a minute is that?" 
 
 Harvey multiplied 5,280 by 4 and divided the product by 60. 
 *'Three hundred 'n' forty-two," he said. 
 
 "Then, if we take the grade at nine per cent the car'U come 
 downw^ard nine-hundredths of three hundred 'n' forty-two feet 
 in a minute; figure that." 
 
 "Thirty feet 'n' seventy-eight-hundredths; practically thirty- 
 one feet," said Harvey. 
 
 "Now, eight thousand pounds dropping at the rate of thirty-one 
 feet a minute is two hundred and forty-eight thousand foot- 
 pounds a minute, ain't it?" 
 
 "Dead sure," agreed Harvey. "You've got a head on you, old 
 man," he added admiringly. 
 
 " 'Tain't me," said the engineer modestly ; "it's Jones' trainin*. 
 Now let's see how it comes out," he resumed. "We've got two 
 hundred 'n* forty-eight thousand foot-pounds a minute to drive 
 the motors as dynamos 'n' overcome the friction o' the car axles 
 
70 
 
 Central Station Experiences. 
 
 Let's get that into watts 'n' then we c'n apply it to the motors bet- 
 ter. Divide that by thirty-three thousand to get it into horse- 
 power 'n' then multiply it by seven forty-six to get it into watts.", 
 
 Harvey scribbled for a few moments and then announced : 
 
 "Five thousand six hundred 'n' six watts." 
 
 '^'Now, have you got that test sheet that Jones gave you when 
 the road was put in ?" 
 
 Harvey produced the test sheet from his wallet and silently 
 handed it over to the engineer. The principal data contained by 
 the test sheet are given in the accompanying table. 
 
 DATA FKOM TEST OF A 30-HORSE POWER 
 
 
 RAILWAY MOTOR. 
 
 
 
 Net Output at 100 
 Rev. of Axle. 
 
 Losses in Watts. 
 
 Amperes. 
 
 
 
 
 
 B. H. P. 
 
 Watts. 
 
 Gears and 
 
 Cores. 
 
 Windings. 
 
 10 
 
 1.65 
 
 1,230 
 
 
 179 
 
 20 
 
 6.28 
 
 4,685 
 
 
 785 
 
 25 
 
 9.47 
 
 6,470 
 
 
 1,260 
 
 30 
 
 11.78 
 
 8,788 
 
 
 1,810 
 
 40 
 
 17.88 
 
 13,340 
 
 1,500 
 
 3,320 
 
 50 
 
 24.6 
 
 18,350 
 
 1,550 
 
 5,400 
 
 60 
 
 32.36 
 
 24,140 
 
 1,760 
 
 7,9-:0 
 
 70 
 
 40 
 
 29,8*0 
 
 1.820 
 
 11,765 
 
 80 
 
 48 
 
 35,800 
 
 
 16,410 
 
 "Your car wheels are 33-inch, ain't they ?" 
 
 Harvey said they were. 
 
 "Then how many revolutions will they have to make if the car 
 runs at three hundred 'n' forty-two feet a minute ?" 
 
 Harvey consulted a table of circumferences in his note-book, 
 scratched away for a few seconds, and announced: 
 
 "Practically forty." 
 
 "Then you won't need any extra resistance coils. See here a 
 moment." Harvey stood beside the engineer and looked over 
 the test sheet with him. 
 
 "The weight o' the car, fairly loaded, gives us five thousand 
 six hundred 'n' six watts of power, on a nine per cent grade at 
 four miles an hour, don't it?" 
 
 Harvey admitted that it did. 
 
 "Now, with twenty-five amperes in the motors each one'll de- 
 velop six thousand four hundred 'n' seventy watts at a hundred 
 revolutions a minute of the axle, or two thousand five hundred 
 
Braking a Car with Its Motors. 
 
 71 
 
 *n' eighty-eight watts at forty revolutions a minute of the axle. 
 That's right, ain't it ?" 
 
 "Accordin' to that sheet it is." 
 
 Harvey stood beside the engineer and looked over the test sheet. 
 
 'Then the two motors'll develop about five thousand one hun- 
 dred 'n' seventy-six watts." 
 Harvey nodded assent. 
 
72 Central Station Experiences. 
 
 "Jones says the iron losses and gear friction don't get much 
 lower than fifteen hundred watts, and the losses in the windings 
 of each motor are twelve hundred 'n' sixty watts, so the total 
 losses in the two motors at twenty-five amperes are about three 
 thousand in the gears and cores and twenty-five hundred in the 
 windings, that's fifty-five hundred watts, or a hundred less'n the 
 weight 'n' speed o' the car give, 'n' a trifle over three hundred 
 watts more'n the motors'll develop at that speed 'n' current. 
 That so?" 
 
 '^Yes, but if the m.otors won't develop that much, where's it 
 comin' from?" 
 
 ''The car '11 take the right speed to make the power developed 
 by the motors correspond with the losses in 'em when they're on 
 short-circuit." 
 
 ''Yes, but what speed'll that be?" 
 
 "We can't figure it exactly from this sheet, but it can't be much 
 faster'n four miles because they almost balance at that speed. If 
 she gets a-goin' at too high a rate you can throw your controller 
 'round to the fourth notch where the resistance is all out." 
 
 Harvey went off up to the car barn in a meditative mood and 
 the engineer did not see him for a week or ten days. Then he 
 came down to the power house, the image of woe, and almost ran 
 over Jones, who was just coming out. 
 
 Who's dead?" asked Jones, with reference to Harvey's de- 
 jected air. 
 
 "Hey? What the . Oh, I didn't recognize you, but I'm 
 
 awful glad you're here. I'm up a stump." 
 
 "Hello, Harvey; how's the brake?" asked the engineer, coming 
 out just at this moment. 
 
 Harvey shook his head gloomily and thrust his hands deep in 
 his pockets. "Don't work at all," he said, "and I'll swear it ought 
 to." 
 
 Jones looked inquiringly from one to the other. "What have 
 you been up to now?" he asked. 
 
 Harvey took out the sketch of the braking connections, handed 
 it to Jones and explained his experiment. 
 
 "You say it's no go ?" 
 
 Harvey nodded and looked hopeful at hearing Jones' doubting 
 inflexion. 
 
Braking a Car ivith Its Motors. 75 
 
 "Did you throw your reversing switch before trying to make 
 the motors brake the car?" 
 
 "Of course not." 
 
 " *Of course not' " mimicked Jones. "How the devil did you 
 expect the motors to generate any current if you didn't ?" 
 
 Both Harvey and the engineer stared at Jones in surprise. This 
 was a totally unexpected development. 
 
 "See here," said Jones, a little impatiently, drawing Fig. 3. 
 
 FIG. 3. 
 
 "You know^ perfectly well that when the motors are running as 
 motors the current passes through from the line in opposition to 
 the counter E.M.F. of the armatures, as these arrows show. 
 Consequently, if you want to make them furnish their own excit- 
 ing current you've got to reverse the connections between the 
 armature and field of each motor — in other words, throw your 
 reversing switch. Then the armature E.M.F. will be in the same 
 direction as that required by the field for its excitation. Do that 
 and your brake'll work like a house a-fire." 
 
 "Well, I'll be d— d!" ejaculated Harvey. 
 
 "Don't doubt it in the least," assented Jones cheerfully. 
 
ENLARGING A RUNNING STATION — 
 THE MOTOR-BALANCER 
 
 "Well, old man," said Jones one day, on the occasion of one of 
 his periodical visitations to the engineer, "I've got a nut for you to 
 crack now/' and he chuckled in his usual boyish fashion at the 
 prospect of "stumping" his hearer. 
 
 The engineer pondered for a moment before replying. 
 
 'Tt's got something to do with the additions that are going in, 
 I'll bet a cookie," he said. 
 
 Jones nodded energetically. "You've struck it, my son," he 
 admitted. "You know that the council has arranged with the 
 Freeport people to furnish lights over there and save 'em the 
 trouble of putting in a plant?" 
 
 The engineer said he did. 
 
 "You also know that your folks are going to put in two i,ooo- 
 light alternators for that purpose and to also take the incandescent 
 load around here?" 
 
 The engineer again acknowledged having been informed. 
 
 "And that we can get only one more engine and generator in 
 here without extending the engine room; also that while there is 
 ample room for extension to the boiler room, this part of the 
 shanty is hemmed in by other property, so that it would be ex- 
 tremely expensive to get more room?" 
 
 "No, I didn't know that." 
 
 "Well, it's so, and the puzzle that confronts you now is to pro- 
 vide for continuous service from the existing plant during the 
 installation of two alternators when you have room only for one, 
 and that without interrupting the service from the present plant 
 a single minute." Jones grinned as he sauntered toward the door. 
 "I'll be back to-morrow and see what sort of solution you have to 
 propose." 
 
Enlarging a Running Station — The Motor-Balancer. 75 
 
 '"Hold on there," called the engineer; ''what's going to be done 
 with these machines that are running now?" 
 
 Jones turned on his heel. "That's part of your problem," he 
 said, and departed. 
 
 The engineer looked at his dynamos, scratched his head, and 
 telephoned to Harvey to come down to the power house. When 
 Harvey arrived he repeated what Jones had said, and looked in- 
 terrogatively at the superintendent for an expression of opinion. 
 Harvey stood staring at the generating plant and the vacant floor 
 space for a few moments, and then took his way into the engi- 
 neer's little den, followed by the owner of the den. 
 
 "One thing's certain," said Harvey, by way of establishing a 
 premise; "you've got to take out your small i lo-volt dynamos and 
 their engine before you can put in the two alternators." 
 
 The engineer assented. "But we can put in one alternator and 
 its engine before disturbing anything at all," he said. 
 
 "Yes; but that won't take care of the no- volt motors that are 
 supplied on each side of your neutral wire," said Harvey. "You 
 can't shut them down, although they amount to a very small part 
 of your motor load now." 
 
 "That's true," agreed the engineer. "But what's going to 
 happen to them after both the alternators are in? These two 
 small dynamos have got to go out, anyhow; and after they are 
 gone I can't run the no-volt motors at all." 
 
 Harvey scrutinized the ceiling, aimed a vigorous expectoration 
 at the mascot cat purring drowsily on top of the engineer's new 
 felt hat, at imminent risk of ruining the headgear, and finally 
 shrunk up in his chair with his own hat pulled down over his eyes 
 and his hands thrust deep in his pockets. The engineer awaited 
 the evolution of Harvey's ideas, cudgeling his own brain mean- 
 while for a solution of the problem. 
 
 "I can't imagine but two ways out of it," finally announced 
 Harvey. 
 
 "Let's have 'em," requested the engineer. 
 
 "Either the no-volt motors '11 have to be replaced by 220-volt 
 ones, or else Jones expects to put in alternating-current motors 
 in their places as soon as the first alternator is in." 
 
 The engineer shook his head dubiously. 
 
 "I don't believe it's as simple as that," he said, "or Jones 
 
7^ 
 
 Central Station Experiences. 
 
 wouldn't have talked about putting in both alternators without 
 disturbing the service. That sounded like he expected to put 
 both of 'em in at the same time." 
 
 "Might 've been tryin' to catch you," suggested Harvey. 
 
 The engineer again signified his lack of assent by a shake of his 
 head. 
 
 "I've been wonderin' if it isn't something like this," he said, 
 drawing a rough sketch like Fig. i. 
 
 L^=^ 
 
 FIG. 1. 
 
 "What the dickens is it?" asked Harvey. 
 
 "A motor-balancer," said the engineer. 'T'm not quite sure 
 about it, but I think they use something like that to balance the 
 two sides of a three-wire system where they have one dynamo 
 connected to the outside wires." 
 
 "How does it work?" 
 
 The engineer looked puzzled. "I'm darned if I know," he ad- 
 mitted, shamefacedly, "but I'm sure that's the kind of a rig I saw 
 described several months ago for doin' that very thing." 
 
 "What is it?" persisted Harvey; "what does it look like life- 
 size?" 
 
 "It's two dynamos or motors exactly alike, with their shafts 
 coupled together." 
 
 "If they're dynamos they must have something to drive 'em," 
 said Harvey. 
 
 "Well, they don't." 
 
 "Then what makes 'em run?" 
 
 "Confound it, I don't know, I told you. If they're motors, I 
 s'pose the line current makes 'em run." 
 
Enlarging a Running Station — The Motor-Balancer. 77 
 
 "What good'll it do to put 'em in, anyway?" 
 
 "Why, they don't take up much room, and I can put 'em any 
 place around the plant without usin' the floor space that the 
 alternators are goin' to take." 
 
 On the following morning there was a solemn conclave in the 
 engineer's den, Jones, Harvey and the engineer constituting the 
 debating body. 
 
 "Well," began Jones, "have you solved the problem ?" 
 
 The engineer hesitatingly produced his sketch and submitted 
 it without a word. Jones glanced at it and beamed. 
 
 "You've hit it first pop," he said; "I'm proud of you. Now let's 
 hear how you propose to go about making the change. I'll tell 
 you this much: the little dynamos are going out for good, both 
 of 'em." 
 
 "I supposed so." 
 
 "Why?" 
 
 "Because there won't be room for both of 'em, and one wouldn't 
 be much good alone." 
 
 Jones patted the engineer approvingly on the shoulder. 
 
 "You won't need me much longer," he said. "Now for the 
 change." 
 
 "Well, I'd put in the motor-balancer first," ventured the en- 
 gineer. 
 
 "Well, what next?" 
 
 "Take out the two small dynamos." 
 
 "Not so fast. Your two small dynamos carry a good-sized part 
 of the load at night, between 5 and 9 o'clock, and a motor-balancer 
 doesn't carry anything; it simply balances out the difference be- 
 tween the two sides." 
 
 The engineer's face fell. 
 
 "Don't give up so easy. Try again." 
 
 "What's the matter with putting in a bigger 250-volt dynamo in 
 place of the one in now ?" suggested Harvey. 
 
 "That'll come later on," said Jones, "but it isn't part of the 
 present plan." 
 
 "What size will the alternators be?" suddenly asked the engi- 
 neer. 
 
 "Fifty kilowatts each," replied Jones. 
 
 The engineer brightened up again. 
 
78 
 
 Central Station Experiences. 
 
 "What a derned fool I am," he said, disgustedly. "The two 
 little machines are 500 lighters, and their engine is a hundred 
 horse-power, indicated. That engine '11 run one of the alterna- 
 tors." 
 
 "Most assuredly," said Jones, encouragingly. "Go on." 
 "We'll have to run the alternating-current primary wiring and 
 put up enough transformers to carry the capacity of one alterna- 
 tor; then put in an alternator in place o' the two little dynamos 
 in the motor-balancer on the 230-volt circuit." 
 
 mmmu 
 
 wnrnm 
 
 "That's first-rate, with a little modification," said Jones. "You 
 see it isn't good practice to put a machine to work on full load the 
 first minute it starts up, so we'll put in an alternator and engine 
 in the spare space first and gradually shift the load from the two 
 small dynamos to the alternator. Then the second alternator can 
 go in in place of the little dynamos." 
 
 "How about the motor-balancer ?" 
 
 "You'd better put that in now, so you can shut down your two 
 small dynamos when the day load is small enough for the 230-volt 
 machine to carry alone." 
 
 "Have you ordered it?" 
 
Enlarging a Running Station — The Motor-Balancer. 
 
 79 
 
 "It's at the freight house now," said Jones, with a grin. "I was 
 keeping it hid until you solved your problem." 
 
 When the motor-balancer came, both Harvey and the engineer 
 regarded it with much curiosity. Neither had ever seen one of the 
 machines in operation, though the engineer, as above related, 
 knew in a general way how it was connected with the circuit. 
 
 Derned if I can see how the thing regulates." 
 
 It did not take much time to install the little machine, and after 
 it was under way the two men bent over it interestedly. 
 
 "Derned if I can see how the thing regulates," said Harvey. 
 "May I see the diagram a minute?" 
 
 Jones handed him a diagram like Fig. 2. 
 
 "Which is the motor?" asked the engmeer. 
 
 "That depends which side of the three-wire circuit has the 
 lightest load," replied Jones. 
 
 "Well, tell us just how the thing works," urged Harvey. 
 
8o Central Station Experiences. 
 
 ''Suppose both sides are equally loaded," explained Jones; 
 ''then both machines will be motors running the common shaft 
 idle. That's clear, isn't it?" 
 
 -''Yes." 
 
 "Now, suppose the side. A, has an increase in load, the electro- 
 motive force across from P to n will be lowered, won't it ?" 
 
 His listeners nodded in unison. 
 
 "Then the armature, a, will tend to run slower than b, but it 
 can't do it because they are rigidly coupled. And b can't slack 
 down because the E.M.F. across from n to N won't let it, so it 
 drives a as a dynamo and the E.M.F. of a is enough higher than 
 that across the line to nearly balance the two sides." 
 
 "Why are the fields cross-connected ?" asked the engineer. 
 
 "To make the balance better. When the E.M.F. across A 
 drops, the field of b is weakened and it speeds up until a balance 
 is obtained. The field of a is kept up by being connected across 
 B, so that the E.M.F. of a can't drop when the circuit E.M.F. 
 across A drops, as it would do if the fields were connected ordi- 
 narily." 
 
 Harvey looked at the engineer, and the engineer looked at 
 Harvey. 
 
 "Simple, ain't it ?" said Jones with bis habitual chuckle. 
 
A SIMPLE TROUBLE WITH ANNOYING RESULTS. 
 
 One of the new alternators had been duly installed in the Mill- 
 ville station and the incandescent load was being transferred from 
 the direct-current circuit to the alternating-current transformers 
 as rapidly as practicable. Jones was in his happiest humor, be- 
 ing submerged with the work of laying out the alternating-current 
 lines and supervising the installation of the transformers. The 
 engineer was in a state of mixed proud satisfaction and nervous 
 apprehension — satisfaction at the substantial increase in the plant 
 under his care, and apprehension of impending dilemmas with 
 which he might not prove quite capable of dealing properly. 
 
 Late one afternoon just after the night load had begun to show 
 up on the ammeter the engineer was surprised by being called up 
 on the telephone by Jones^ from the hotel. 
 
 "What the deuce ails your alternator?" asked Jones. 
 
 "Nothing that I know of," replied the engineer. "What's wrong 
 up there?" 
 
 "Lights all dim," reported Jones. "Look at your voltmeter." 
 
 The engineer did so. 
 
 "It was about half a volt low," he called to Jones through the 
 telephone. "I've raised it to half a volt high; how do they look 
 now?" 
 
 "Bare trifle better," replied Jones, "but they're not up by a good 
 deal. See if there are any loose connections beyond the voltmeter, 
 back of the board." 
 
 The engineer made a careful inspection of the feeder wires be- 
 yond the voltmeter, but could find nothing irregular and so re- 
 ported to Jones. 
 
 "I've tested up here while you were gone from the 'phone," 
 said Jones, "and the voltage is only 97J now. You'll have to give 
 
82 Central Station Experiences. 
 
 your rheostat a twist and run about three vohs high to-night. I'll 
 come down in the morning — too tired now." 
 
 The engineer did as Jones suggested, and spent an uneasy- 
 night as a result of the trouble. Before leaving the station he ex- 
 amined every main connection about the alternator and the 
 switchboard, as well as all of the exciter dynamo connections. 
 Every one was perfectly tight and normal. 
 
 The next morning the engineer was at the station bright and 
 early, and Jones arrived soon after, with a placid smile that reas- 
 sured the engineer greatly. 
 
 "Found it?" asked Jones. 
 
 The engineer shook his head despondently. 
 
 "You'll find it in one of two places," asserted Jones confidently. 
 
 The engineer looked at Jones interrogatively. 
 
 "It's either a loose compensator connection or a bad joint or 
 connection at the lightning arresters. Sure you looked over the 
 switchboard connections carefully?" 
 
 "Dead sure. I went over 'em four or five times." 
 
 "Didn't notice the compensator?" 
 
 "No; the voltmeter connections were all right though." 
 
 "Try the lightning arrester connections ?" 
 
 The lightning arresters were up in a feeder tower on the roof. 
 "No"; admitted the engineer, "I didn't." 
 
 "Compensator's less trouble to get at. Let's look at it first." 
 
 The engineer brought a step-ladder and Jones ascended it and 
 took the cover ofif the compensator. Then he turned and looked 
 down at the engineer, chuckling. 
 
 "Told you so," he said, holding the loose end of a wire gingerly 
 between his fingers. Then he switched the compensator out of 
 circuit, put the loose wire in the terminal post, and switched the 
 instrument back in circuit. The voltmeter needle immediately 
 fell back about two volts, and Jones executed a triumphal descent 
 from the top of the ladder, narrowly escapin-g a tumble in the per- 
 formance. 
 
 "Is it all right now ?" asked the engineer. 
 
 Jones nodded. "See your voltmeter needle drop?" he asked. 
 "Sorry I didn't get a chance to explain this to you before." 
 
 The two went into the engineer's little room and Jones pro- 
 duced from his wallet a sheet on which was a diagram like Fig. i. 
 The engineer hung over his shoulder in eager anticipation. 
 
A Simple Trouble with Annoying Results. 
 
 85 
 
 "The voltmeter is supplied by a little transformer," said Jones, 
 "which reduces the line voltage to the regular lamp voltage, so 
 that the voltmeter indicates the lamp voltage instead of the line 
 voltage. You knew that, of course." 
 
 Jones executed a triumphal descent from the ladder. 
 
84 
 
 Central Station Experiences. 
 
 "Yes." 
 
 "Well; now, in order to avoid using pilot wires from the center 
 of distribution back to the station voltmeter, this compensator is 
 used." 
 
 The engineer nodded. 
 
 "The voltmeter solenoid has two coils; the main coil is con- 
 nected to the transformer and the other one to the compensator." 
 
 "Yes." 
 
 "The compensator is a transformer with an adjustable primary 
 winding in series with the main line and an adjustable secondary 
 which is connected with the auxiliary coil on the voltmeter." 
 
 "How is the winding adjustable?" 
 
 Jones sketched Fig. 2. 
 
 "Each winding has a lot of taps, so that the number of turns in 
 the primary circuit may be varied by shifting the plug, and the 
 number in the secondary varied by moving the switch." 
 
 "What is the object of varying 'em." 
 
 "To 'compensate' for different line drops and to adjust for dif- 
 ferent strengths of primary currents." 
 
A Simple Trouble with Annoying Results. 
 
 85 
 
 "How does the thing compensate for drop?" 
 
 *'It doesn't literally compensate for the drop. The auxiliary 
 coil on the voltmeter which is fed from the compensator opposes 
 the main coil, and the amount of opposition is such that the needle 
 falls back exactly the amount of your line drop. Therefore, when 
 you strengthen your alternator field and bring the needle up to 
 where it indicates 100 volts, the line voltage is raised just enough 
 to make up for the drop and deliver the normal E.M.F. at the far 
 end of the feeder." 
 
 The engineer looked rather confused. 
 
 1 lu »tn^^ 
 
 ! noooooooofio 
 
 FIG. 2. 
 
 ''Don't you see it?" 
 
 ''Not quite." 
 
 Jones scratched his head rather impatiently. 
 
 "Suppose your line drop is five per cent. If the compensator 
 were left out, your voltmeter would indicate a hundred when in 
 reality the E.M.F. uptown at the lamps was only ninety-five. 
 That's clear, isn't it?" 
 
 "Of course." 
 
 "Now, with the compensator in, and full load on, the main-line 
 current going through the primary of the compensator induces a 
 current in the secondary that weakens your voltmeter solenoid 
 just enough to make the instrument indicate five per cent short. 
 
86 Central Station Experiences. 
 
 Consequently, it indicates what the voltage is at the lamps and all 
 you have to do is to bring up your E.M.F. until the needle indi- 
 cates 100. See?" 
 
 "Yes, but how about varying loads ?" 
 
 "If the full load drop is five per cent, the drop with half load 
 will be two and a half per cent, won't it ?" 
 
 "Certainly, but the compensator is set for " 
 
 "Never mind that. At full load the compensator weakens your 
 voltmeter five per cent. Now, as the compensator primary is in 
 series with the line, at half load the current in it is only one-half 
 the full load current, consequently its secondary effect is only one 
 half " 
 
 "So that the voltmeter is weakened only two and a half per cent, 
 the same as the drop; I see. But if the compensator wire was out 
 of the terminal last night why didn't it open the circuit?" 
 
 "Because it was the small wire leading to the voltmeter coil 
 and not the main wire." 
 
 "So that it merely disconnected the small coil on the voltmeter 
 and left it indicating the E.M.F. at the switchboard instead of the 
 voltage at the lamps uptown ?" 
 
 "Precisely so." 
 
TRANSFORMERS ON THREE-WIRE SECONDARIES 
 
 ''Harvey, do you know anything about transformers?" asked 
 the engineer one afternoon as the railway superintendent wan- 
 dered into the Httle den at the power house. 
 
 "Divil an atom," disclaimed Harvey, with cheerful indifference. 
 "Do you?" 
 
 The engineer shook his head slowly, leaned back and deposited 
 both feet upon the testing bench. "I thought I did know how to 
 connect 'em up together," he said; *'not that I had much confi- 
 dence in my ability to tinker with alternat'n stuff, but I sure did 
 think I could hitch up two transformers together." 
 
 "Well, what's shook your faith?" 
 
 "Why, IVe had two of 'em workin' together up at the sash 
 factory near the junction 'bout a week, 'n' one of 'em's burnt out 
 twice, with pretty near no load; don't even blow the fuses." 
 
 "Sure 'twas all right when it went in?" 
 
 The engineer nodded emphatically. "First one w^as bran new; 
 second one was tested all over before it went out there." 
 
 "How'd you have 'em connected up ?" 
 
 "Primaries in series, 'n' secondaries three-wire." 
 
 "Thought the primaries had to go in parallel always?" 
 
 "They do, gen'rally ; but the 2000-volt line don't run out there. 
 The 4,000-volt feeder goin' over to Freeport runs right past the 
 mill, 'n' I put two 2,000-volt transformers there in series." 
 
 "Why 'n't you put a 4,000-volt transformer there?'* 
 
 "Got none." 
 
 "What do you use over at Freeport?" 
 
 "The voltage comes down to 2,000 right at the blast furnace 
 corner. Step-down transformer there, you know." 
 
 "No, I don't know; never heard of one." 
 
38 Central Station Experiences. 
 
 "Well, it's simply a special 25-kilowatt transformer that brings 
 the 4,000 volts down to 2,000." 
 
 "So you use ordinary transformers over there?" 
 
 The engineer nodded. 
 
 'What'd you say happened at the sash factory ?" 
 
 "They got to cutt'n' up monkey shines a couple o' days ago 
 and blew the biggest of the secondary fuses on one side o' the 
 circuit. There were two or three lamps left burnin' on that side, 
 'n' they busted. The lamps on the other side went out. Just after 
 I got there the transformer on the damaged side begun to smoke 
 'n' I saved the other one by pullin' the primary switch. Same 
 thing happened yesterday again." 
 
 Harvey looked sympathetic but helpless. 
 
 "Several persimmons too high for me," he said. "Did you ask 
 Jones about it ?" 
 
 "Not yet. He's due here to-night, but I hate to be all the time 
 runnin' to him like a baby." 
 
 "You're in dead luck to have him to run to," observed Harvey. 
 ^'You'd find it kinder tough pullin,' sometimes." 
 
 "That's all so," admitted the engineer, "but ain't I ever goin' to 
 get so's I c'n paddle my own canoe a few feet without gettin' on a 
 
 TOCk?" 
 
 Harvey grinned. 
 
 "Seems to me you must be graduated pretty soon," he said, 
 ''You've had about all the stunts on the programme, ain't you ?" 
 
 The engineer assented and rose to go out. 
 
 "Where to, now?" asked Harvey. 
 
 "Goin' to meet Jones. I won't sleep any to-night if I don't get 
 at the bottom o' this derned thing." 
 
 Jones arrived duly, and the first thing that met his gaze was the 
 woebegone face of the engineer. 
 
 "Hotel's the nearest," said he, interpreting at once the general 
 meaning of the engineer's countenance. "You can tell me all 
 about it while I eat supper." 
 
 The engineer restrained himself until Jones had made consider- 
 able progress with his meal, knowing that he would get more 
 satisfactory attention by doing so. Then he recited the experi- 
 ence alreadv related to Harvev. 
 
Transformers on Three-Wire Secondaries. 
 
 89 
 
 "Hm-m," said Jones. 'That's a sort of knocker. Draw me a 
 rough diagram of the transformer connections and fuses." 
 
 The engineer drew Fig. i, and Jones added the reference letters. 
 
 ''Fuse blew at x in the leg X, and cut out the lamps on h?'* 
 asked Jones. 
 
 "Yes; that left only two or three lamps on the B transformer, 
 from the other branches, 'n' they all busted." 
 
 cmwf^r-n-mwsfi 
 
 yi 
 
 tt-o 
 
 Ajte\ 
 
 -k^^^Caz 
 
 (hvt- 
 
 l^^ACrr 
 
 iriiC". 
 
 FIG. 1. 
 
 "And how many larrips were on A V 
 
 "About twenty-eight or thirty." 
 
 "They're forty-light transformers, ain'i they ?" 
 
 "Yes." 
 
 "No fuses blow at Ur 
 
 "No." 
 
 "Primary fuses all right?" 
 
go Central Station Experiences. 
 
 "Sound as a dollar." 
 
 Jones knitted his brows ferociously and gazed intently at the 
 diagram. "Thirty lights on A and three on 5," he muttered, 
 "You say the B transformer was the burnt one ?" he asked. 
 
 "Yes," said the engineer; "just baked to a crisp." 
 
 "Hm-m. Guess you'd better leave that with me over night," 
 said Jones. "I'll see if I can shift it by bed-time." 
 
 The engineer brightened up. "Then it ain't a simple trouble?" 
 he asked. 
 
 Jones shook his head vigorously. 
 
 "One of the meanest I've run across in some time," he said. 
 
 The engineer went home and slept soundly, feeling satisfied 
 that he could not be considered hopelessly ignorant for failing to 
 solve a problem that gave Jones so much trouble. 
 
 Bright and early in the morning Jones was at the station, and 
 his beaming visage told the engineer before he got fairly in the 
 door that the problem was solved. 
 
 "My boy," said Jones^ with mock solemnity, "I'm an ass. I 
 should have found your trouble immediately, but it took me until 
 one o'clock last night." 
 
 "What on earth was it?" asked the engineer. 
 
 "Heating of the core. You know that the heating of a trans- 
 former core due to the reversals of current increases faster than 
 the voltage, when the voltage is raised, don't you?" 
 
 "Ye-es," said the engineer hesitatingly, "but I don't know 
 much about that yet." 
 
 "Well, I'll tell you. The heating due to core losses increases 
 almost as the square of the voltage; that is, at twice the proper 
 voltage the core loss heat is a little over three times the heat at 
 normal voltage." 
 
 "Well; but the voltage didn't change." 
 
 "Don't get excited. You know that as the load on the second- 
 ary of a transformer increases, its primary back E.M.F. decreases, 
 allowing more current to flow in the primary ?" 
 
 "Yes." 
 
 "Therefore, when most of the load was removed from B by 
 blowing the fuse, its counter E.M.F. at the primary end became 
 much higher than that of A, which remained loaded." 
 
 "Yes." 
 
Transformers on Three-Wire Secondaries. 
 
 91 
 
 "The primary of A tried to pass a considerable current, increas- 
 ing the back E.M.F. of B, so that it was about three times that 
 of^." 
 
 "Well ; I should think that would keep down the primary cur- 
 rent and the heating." 
 
 "Yes, it kept down the primary current, but the heating wasn't 
 due to that. You know that the counter E.M.F. of a transformer 
 
 Jones knitted his brows ferociously and gazed intently at the 
 
 diagram. 
 
 is equal to the impressed E.M.F., minus the extremely small drop 
 due to resistance?" 
 
 "Yes." 
 
 "Well, the resistance drop is too small to count. However, no 
 matter what the drop is, if the counter E.M.F. of B was three 
 times that of A, which is entirely probable, the impressed E.M.F. 
 divided itself between them in precisely the same ratio — three to 
 
92 Central Station Experiences. 
 
 one — and the result was the same as though you had put the B 
 transformer on a 3,000-volt circuit." 
 
 The engineer gazed at Jones and emitted a long whistle of 
 amazement. 
 
 "What broke the lamps?" he asked. 
 
 "The secondary voltage of B rose with the primary voltage ; if 
 the primary had 3,000 volts the secondary had 150, instead of the 
 usual 100. The breaking of the lamps removed all the load from 
 the B transformer, raising its counter E.M.F. still more, and 
 making the core heat worse." 
 
 "Well, what'll I do about lighting the factory?" 
 
 "Put just as small fuses in the neutral wire as you can— not 
 over half the size of the outside fuses at each cut-out. Then if an 
 outer fuse goes, the current rush in the neutral will blow the 
 neutral fuse and both sides will be thrown out." 
 
A LONG CIRCUIT FROM ORDINARY GENERATORS. 
 
 TWO-PHASE MOTORS ON SINGLE-PHASE 
 GENERATORS. 
 
 "Young man," said Jones to the engineer one day, "I'm going 
 to give you a chance to shine." 
 
 The engineer looked apprehensive. 
 
 "Is it goin' to be very hard ?" he asked, knowing that Jones had 
 some unusual problem in store for him. 
 
 '"Well," drawled Jones, "it's not so darned easy; but I believe 
 you can do it if you buckle down to it." 
 
 "What is it?" 
 
 "You know that a feeder's got to be run across the river to 
 Perkins' mill and the little yarn factory for lights and three or four 
 big motors, don't you?" 
 
 The engineer nodded assent. 
 
 "Well, the distance is too great to deliver direct current, even 
 if you could put poles across in the river, to hold up heavy wires, 
 which you can't; therefore we've got to use the alternating cur- 
 rent, and even at that it's going to be somewhat of a problem to 
 get over and deliver enough voltage at the other end. I'm going 
 to let you figure out the way to do it." 
 
 "How much drop do you intend to allow?" 
 
 "Not over 5 per cent from the switchboard right to the en- 
 trances of the two mills. That means delivering about two thous- 
 and volts." 
 
 "Let's see; there'll be ninety-hundred 'n' ten — twenty-two — a 
 hundred and twenty-two lamps in one mill and about forty in the 
 
 other. The motors '11 add up about — " here he stopped to 
 
 make a rough calculation "Whew! There'll be about sixty 
 
 amperes in the primary circuit." 
 
94 Central Station Experiences. 
 
 "Right," said Jones. "Then what?" 
 
 "Why the mills are a good two miles from here!" 
 
 "Well ?" 
 
 The engineer drew his "reference book" from his pocket and 
 consulted a wiring table that Jones had given him when the 
 alternating-current plant was installed. 
 
 "The line figures up six hundred 'n' thirty thousand ampere- 
 feet," he said, "and No. oo wire will only take six hundred 'n' five 
 thousand ampere-feet at 5 per cent drop." 
 
 "Exactly," agreed Jones. "This is where your chance to shine 
 comes in." 
 
 The engineer scratched his head dubiously. 
 
 "No. 00 wire won't hang up across that river," he said, with a 
 perplexed glance through the window at the offending stream. 
 ^Tt's at least a thousand feet across." 
 
 "Then you can't use No. 00 wire, of course," said Jones, sug- 
 gestively. 
 
 The engineer looked at him steadily for several minutes, but 
 Jones' countenance gave no clue to a solution of the problem. 
 Suddenly the engineer bethought him of the line running over to 
 Freeport, on which the potential had been raised to 4,000 volts 
 by means of a step-up transformer, and he fairly beamed as he 
 blurted out: 
 
 "Step-up transformer!" 
 
 Jones shook his head quizzically. 
 
 "Game ain't worth the candle," he said. "You're too extrava- 
 gant." 
 
 The engineer looked crestfallen, and Jones hastened to reassure 
 him. 
 
 "You're not so far out of the way," he said; "don't get dis- 
 couraged so quickly. What would you do in the case of a railway 
 feeder that had too much drop ?" he continued, in order to help 
 the engineer along. 
 
 "Put in a boost — well, I'll be jiggered," in high disgust; "I did 
 think I had more sense 'n to take all day to a thing as simple as 
 that." 
 
 Jones grinned cheerfully. 
 
 ''What kind of a booster would you use ?" asked he. 
 
A Long Circuit from Ordinary Generators 
 
 95 
 
 ''Transformer, of course," said the engineer promptly, drawing 
 a commendatory series of vigorous nods from Jones. 
 
 "All right so far," said the latter. '^'Now draw me a diagram of 
 your transformer connections and figure out the size of your 
 wires." 
 
 The engineer drew the diagram shown by Fig. i, handed it 
 over to Jones and waited for a verdict. 
 
 "Correct," said Jones. "That raises your voltage to " 
 
 "Twenty one hundred/' cut in the engineer. 
 
 "Not exactly. Remember that your switchboard voltage is 
 over two thousand; you are delivering two thousand to your 
 transformers uptown. What is the switchboard voltage ? About 
 twenty-one hundred, ain't it ?" 
 
 "Twenty-one hundred 'n' ten at full load." 
 
 Mai 
 
 ^WM 
 
 FIG. 1. 
 
 "Then the booster will raise you to twenty-two hundred and 
 ten, and you have a margin of two hundred and ten volts for your 
 drop in order to deliver two thousand volts at the mills. Remem- 
 ber, though, that the most of your drop must go in the wires 
 across the river because they must be small." 
 
 "I can run steel cables across to hang the copper wires from," 
 suggested the engineer. 
 
 "That's good; but your copper wires must be pretty small so 
 that they won't break down the steel ones." 
 
 The engineer spent several minutes figuring on the tensile 
 strength of steel cables, the weight of line wires, etc., and finally 
 drew a long breath. "It won't be safe to run anything bigger 'n' 
 a No. 8 wire across there hung on steel rope," he said, "unless I 
 use a rope as big as my arm." 
 
 Jones nodded and said not a word. 
 
g6 Central Station Experiences. 
 
 "'No. 8 wire," continued the engineer, ''eleven hundred feet 
 long with a load of sixty amperes, has sixty-six thousand ampere- 
 feet, 'n' that means a drop of 4 per cent right there." 
 
 "How many volts of drop is that?" asked Jones suggestively. 
 
 ''Oh, that's so; it's only eighty volts, 'n' we've got a margin of 
 two- hundred 'n' ten/" brightening up. "Why, that's a cinch. I 
 c'n put in just as big wires as I please on the other side o' the 
 river, so's to keep the total drop down to two hundred 'n' ten." 
 
 "That's all right, so far," said Jones. "You can work out the 
 land wires any time, but you mustn't forget that the self-induction 
 of the line itself will increase your drop considerably — about two 
 or three per cent of the drop itself. Now you've got the right idea 
 it won't be any trouble for you to get that fixed up all right. 
 The next thing is to consider how you're going to arrange about 
 the motors across in the mills. Then again, you want to arrange 
 to cut out your booster transformer every night after the motors 
 have been shut ofif so you won't be pumping juice through the 
 booster and wasting that much energy; besides, with only the 
 night lamps in circuit over there you can't have such a high volt- 
 age as the booster would give." 
 
 "Easy enough to cut out the booster," said the engineer. 
 "Simply put a switch in the primary and cut her out with it." 
 
 Jones handed him back the diagram. 
 
 "Look at your connections again and see if you think that'll 
 cut it off," he said. 
 
 "The secondary '11 be in series with the line," said the engineer, 
 "but it hasn't enough resistance to amount to anything." 
 
 "No; but the resistance doesn't amount to anything much any- 
 how," said Jones. "Your secondary has exactly the same effect 
 on the core that the primary has, and with the primary open the 
 core losses '11 keep on just the same. Worse still, the secondary 
 acts as a choking coil if the primary is open, and it would cut 
 down the voltage on your line, even with a very small load going 
 through. Draw me a diagram of an arrangement to cut out both 
 the primary and secondary at one operation with a single switch 
 and without opening the line." 
 
 The engineer labored mentally for awhile, and finally produced 
 the diagram shown by Fig. 2. 
 
 "Good boy," said Jones heartily. "Now for the motor business." 
 
Tii-0-phasc Motors on Single-phase Generators. 97 
 
 "That's one too many for me," said the engineer positively. "I 
 
 dunno a thing about 'em. Didn't know they used motors on 
 single-phase lines." 
 
 The engineer got up and fairly danced in h\s admiration. 
 
 "Yes; they do, all right; but we're not going to run any single- 
 phase motors around here!" 
 The engineer looked puzzled. 
 "Aren't the alternators single-phase machines?" he asked. 
 
98 
 
 Central Station Experiences. 
 
 ''Yes ; but there are two of them. See ?" 
 
 The engineer didn't see for some Httle time. Then he gave vent 
 to a long whistle. "Well, I'll be " 
 
 ''No, you needn't," interrupted Jones; "you've been jiggered 
 once to-day. What's the matter?" 
 
 "You're goin' to run a two-phase circuit off'n the two alterna- 
 tors, ain't you?" 
 
 "Precisely; why not?" 
 
 "How'll you keep the two phases right ?" 
 
 "Couple the shafts with a sliding dental clutch, made so that 
 they can't couple but one way — exactly right to give two phases 
 a quarter of a cycle apart." 
 
 FIG. 2. 
 
 The engineer got up and fairly danced in his admiration. 
 
 "Gee whiz ! what a scheme," he exclaimed. Great Moses ! then 
 we c'n supply two-phase motors all around the edge o' town 
 where it's too far for the direct-current Hues to run. Sufiferin' 
 snakes ! won't that take Harvey's hat ofif !" 
 
 "How's that?" 
 
 "He's been crowin' aroun' here for a week, threat'nin' to put 
 in 500-volt motors in the little factories out on the fair ground 
 branch 'cause I wouldn't run the power circuit out there. Now 
 IVe got him. But, say," suddenly sobering down, "won't al- 
 ternat'n'-current motors knock out the voltage on that line across 
 the river?" 
 
 "You mean make the drop worse?" 
 
 The engineer nodded 
 
 "It might if we used induction motors alone, but I'm going to 
 
Two-phase Motors on Single-phase Generators. 99 
 
 put synchronous motors in the yarn tactory and adjust 'em to 
 neutralize the effect of the induction motors in Perkins' mill. 
 Tell you about that next time I come down." 
 
 L.ofC. 
 
INCREASING THE OUTPUT OF AN ALTERNATOR. 
 WIPING OUT INDUCTIVE DROP. 
 
 The plant at Millville had run along for several months "with- 
 out even an incident," as Harvey expressed it, when Jones ap- 
 peared in the doorway of the engineer's ''den" one morning and 
 asked : 
 
 "How fast is your load growing?" 
 
 The engineer, having become accustomed to Jones' methods of 
 attack, merely reached for his station record book, consulted it, 
 and replied: 
 
 "Mighty slow, if at all. We've got about everything there is 
 except the little cotton mill." 
 
 "Well, you'll get that soon. I've practically sold 'em the mo- 
 tors." 
 
 The engineer scratched his nose reflectively. 
 
 "How much power'U they want?" he asked. 
 
 "About 25 horse-power." 
 
 "Can't pull 'em." 
 
 "You'll have to," asserted Jones, with a grin. 
 
 " 'Nother problem ?" queried the engineer. 
 
 Jones nodded. 
 
 How much do you lack of full load on the alternators?" he 
 asked. 
 
 "About five amperes on the switchboard ammeter." 
 
 "That's about 11,000 watts; say 10,000 watts available." 
 
 The engineer assented. 
 
 "That means about 13 horse-power," continued Jones. "Now, 
 your engines and boilers are big enough for a considerable in- 
 crease in load beyond the capacity of the alternators; I took care 
 of that when thev went in." 
 
Increasing the Output of an Alternator 
 
 lOI 
 
 "That's right," agreed the engineer, ''but that don't help the 
 alternators out, does it?" 
 
 "Xo, but it enables us to help 'em out," said Jones. 
 
 The engineer scratched his nose reflectively. 
 
 "Change 'em for bigger ones?" asked the engineer. 
 
 "Nope." 
 
 "Rewind the armatures with heavier wire and run 'em faster?" 
 
 "No; that would run your frequency up too high." 
 
102 Central Station Experiences. 
 
 The engineer looked through the door at the alternators; then 
 at Jones' imperturbable countenance. Then he blew his nose in 
 a helpless sort of fashion and said: 
 
 'T give it up." 
 
 Jones sniffed disappointedly. 
 
 'T thought you were gamer than that," he said. 
 
 'TVe guessed the only ways I know to raise the capacity," said 
 the engineer, somewhat abashed. 
 
 "No, you haven't," said Jones. *'You know the way to do it 
 perfectly well, but you haven't remembered it, that's all." 
 
 The engineer was more puzzled than ever. 
 
 "It's a case of changing something, of course," continued Jones. 
 "The output of a machine can't be increased without making a 
 change in it somewhere." 
 
 "There's nothin' to change but the armature that'll change the 
 output," suggested the engineer. 
 
 "Certainly not — at least, in a machine already built." 
 
 "Well, I don't see how it can be changed to give more current 
 without rewinding it." 
 
 "Or substituting another armature with a different winding," 
 said Jones. "You're slow to-day." 
 
 The engineer thought it over until he was nearly addled, and 
 finally suggested timidly: 
 
 "Two-phase armature?" 
 
 "Of course; you know as well as I do that a two-phase armature 
 has more output than a simple winding, because the wires fill all 
 of the space around the whole armature surface. How much of 
 the circumference is occupied by wires in your single-phase arma- 
 tures ?" 
 
 "About four-fifths." 
 
 "Then if you have two windings, each covering half of the 
 armature, you'll have " 
 
 "One-fifth more wire than there is now," broke in the engineer. 
 
 "Your arithmetic is bad." 
 
 The engineer stared. 
 
 "Suppose it took five hundred wires to cover the armature," 
 said Jones, "your single-phase armature would have about four 
 hundred, eh?" 
 
 "Yes." 
 
Increasing the Output of an Alternator 
 
 103 
 
 **Now, if you add the other hundred, is that adding only a 
 fifth?" 
 
 *'Guess I must be 'dopey,' " said the engineer, sheepishly. "Do 
 you mean a two-phase armature '11 give a fourth more output 'n a 
 single-phase, same size?" he asked. 
 
 "No," said Jones, ''it won't. I was only correcting your arith- 
 metic. But it'll give about eighteen or twenty per cent more 
 output, and that'll be a-plenty to carry all the load you'll get for 
 six or eight years." 
 
 r,2 PHASE FEEDER 
 
 3 
 
 OLD 
 
 ^4- 
 
 BUS BARS 
 
 dcma 
 
 (p (I) (pep 
 
 t^-i 
 
 □ □dd 
 
 TO ALTERNATOR 
 FIG. 1. 
 
 TO ALTERNATOR 
 
 "How'll we connect the machines at the board?" asked the 
 engineer. 
 
 "Divide up your single-phase circuits between the two phases 
 and use one pair of your bus-bars for one phase and the other pair 
 for the other phase." 
 
 "And run the machines together?" 
 
 "Yes; this way," and Jones drew Fig. i. "You see, you won't 
 have to change a thing on the face of the board except the alter- 
 nator main switches. The feeders can be divided between the two 
 
I04 Central Station Experiences. 
 
 phases on the back of the board. We'll have to put in synchroniz- 
 ing lamps so you can tell when to throw the switch." 
 
 In the course of a few weeks the change was made and Jones 
 took advantage of a light-load part of the day, when only one 
 alternator was needed, to show the engineer how to put the two 
 machines in parallel. He started up the second machine and threw 
 it in circuit with the working alternator, then cut it out and shut 
 down, going through this process several times so that the object 
 lesson might be thorough. Then he turned the machine over to 
 the engineer for a trial. 
 
 The first attempt was successful, but the engineer was so excited 
 that his knees almost wobbled. Cutting out the machine, he sig- 
 naled his assistant at the engine throttle to close down and open 
 up again. The phasing lamps began to flicker as the alternator 
 approached synchronism, the flickering becoming slower and 
 slower, slower and slower, until the engineer in his nervousness 
 closed the switch just as the lamps weitt out."^ There was an ear- 
 splitting screech from the belts, a subdued roar from the armatures 
 and a final bang from the fuses ; the boy at the throttle fled in- 
 continently, Jones walked coolly to the engines and shut them 
 both down, and the engineer leaned weakly against the switch- 
 board. 
 
 "Get a move on and put in fresh fuses," called Jones, who was 
 rapidly looking over the alternators. 
 
 The engineer did so, opened the alternator switches, and started 
 up the engines again, Jones having found no signs of damage. 
 Nothing had been harmed, and after a few more "object lessons" 
 by Jones the engineer became more confident and performed the 
 operation of "coupling up" several times without a "misfire." 
 
 "All you need's a little more nerve," said Jones. "Now, let's go 
 inside while I tell you about those synchronous motors across the 
 river." 
 
 They went into the engineer's little room, and Jones put his 
 feet on the desk, preparatory to delivering his homily. 
 
 "You know, of course, that in an alternating-current circuit 
 the current constantly reverses, passing from nothing to maximum 
 in one direction and back to zero, then to maximum in the opposite 
 
 * In some plants the phasing lamps are connected so as to show no light when the 
 alternators are in phase, in this narrative the opposite condition is assumed, t. e., 
 the lamps light up when the alternators are in phase. 
 
Wiping Out Inductive Drop. 105 
 
 direction and back to zero, then in the first direction, and so on." 
 
 The engineer said he understood that. 
 
 "Do you know, too, tliat the current in a circuit does not always 
 reverse its polarity at the same instant with the reversal of the 
 E. M. F. of the circuit?" 
 
 "I know it's so, but I don't understand why," said the engineer. 
 
 "Well, that lagging of the current reversal behind the voltage 
 reversal is caused by self-induction in the circuit." 
 
 *'When magnets are used in a circuit?" 
 
 ''Yes. A coil of wire without any core has a good deal of self- 
 induction, but when it has a core it is hundreds of times worse. 
 Now, do you know what electrostatic capacity is ?" 
 
 ''N — no. I've read about it, but it's too rich for my blood." 
 
 ''Well, you don't need to be a scientist to run a plant. Capacity, 
 as it's called for short, is almost the opposite of self-induction — 
 electricians call it negative reactance, and reactance is the result of 
 self-induction." 
 
 "Yes ; I know that much." 
 
 "All right. Now, capacity has the opposite effect on the relation 
 between E. M. F. and current from that of self-induction — it 
 pulls the current ahead of the voltage so that it actually reverses 
 ahead of it. Now, you can easily see that if inductance or self- 
 induction pulls the current reversals back — retards them — and 
 capacity pulls them ahead — advances them — it is possible to bal- 
 ance one by the other and have your current reverse precisely with 
 theE. M. F. See?" 
 
 The engineer "saw," and expressed his admiration. 
 
 "Now, a synchronous motor can be made to give a circuit elec- 
 trostatic capacity, but an induction motor always gives it self- 
 induction or reactance, whichever you choose to consider." 
 
 "What's the difference?" broke in the engineer. 
 
 "Why, you know. Self-induction is the cutting of magnetic 
 lines by the wires of the coil that produces the magnetic lines. 
 Reactance is the opposition which this process offers to the pas- 
 sage of current through the coil, just as resistance is the opposition 
 of the wire itself to the passage of current. Now, let's get back. 
 If you have induction motors on a line, they introduce a lot of self- 
 induction, and make the reversals of current lag behind the re- 
 versals of E. M. F. If you add synchronous motors to the circuit 
 
lo6 Central Station Experiences. 
 
 and adjust them to give a capacity effect, you can neutralize the 
 self-induction and get rid of that lag." 
 
 "How do you adjust them for capacity?" 
 
 ''Strengthen the field-magnets beyond the point necessary for 
 ordinary working." 
 
 The engineer gazed thoughtfully at Jones' sparse forelock and 
 remembered the care with which his instructor had adjusted the 
 fields of the synchronous motors in the mill across the river. He 
 was aroused by the banging of Jones' heels on the floor as he 
 abandoned his lounging attitude and arose. 
 
 "Well, my boy," said Jones, as he struggled into his overcoat, 
 "I'm going to leave you alone for a long time now. I've about 
 worked out the field around here, and you've got to a point where 
 you don't need any help, except in case of some very unusual 
 trouble. 
 
 "Always remember to keep cool, no matter what happens. If 
 anything goes wrong, think it over first and get scared afterwards. 
 Any time you get into a serious hole, telegraph me at the home 
 office and I'll come as soon as possible. But don't get rattled. 
 Good-by," and with characteristic abruptness Jones grabbed the 
 engineer's hand vigorously and was gone. 
 
 The engineer watched his going with a heavy heart and feeling 
 as though a large part of the earth had been suddenly snatched 
 away immediately in front of him, leaving him tottering on the 
 edge of a chasm. 
 
.Tnne-O. IdOl 
 
MAY 31 1901