Electricity experimentally and practically applied; a book for the beginner and for the practical man, principles, experiments, practical applications and problems

Front matter

Class ^J^'fe^

GopigteE"

COPYRIGHT DEPOSm

Preface

Although a number of excellent works on practical electrical engineering are already in use, the author believes there is a place for a volume that will present the subject from an experimental standpoint. For many years the author has taught the subject of electrical engineering by means of experimental lectures and laboratory work to large numbers of practical men. Since these students have often lacked mathematical training, it has been necessary to explain the subject-matter in a very simple way, showing, wherever possible, its practical features. The same method of presentation has been used in this text, and it is hoped that a much larger audience may thus be reached and benefited. This volume is particularly adapted to courses of instruction given to those engaged in actual electrical work ; it should likewise prove useful as a text for high schools and for college laboratory courses.

Owing to the manner in which the experiments are arranged in the text and the detailed descriptions given this volume should prove helpful to the self-taught individual.

The author has assumed at the outset, as in his lectures, that the reader is familiar with certain practical terms. This assumption is justifiable, since most beginners, if at all interested in their subject, are likely to have acquired a knowledge of general facts before they have begun the systematic study of the subject. Practical men in particular have a much greater knowledge of funda-

VI PREFACE

mental principles than they are ordinarily given credit for. Later in the text such terms are defined in detail. The explanations of experiments usually give the details for their performance before an audience, as experiments thus performed are much more difficult than those made in a laboratory. If any experiment is to be performed by a single individual, however, as in a laboratory, the author has trusted to the reader's originality to omit superfluous apparatus.

In looking over the experiments it may be noted that a number of them are modifications of standard experiments such as those on induction developed by Faraday. There is, however, a large number of new experiments given. These experiments were developed in connection with educational courses given to the employees of the Brooklyn Rapid Transit Company, the Edison Illuminating Company of Brooklyn, the New York Edison Company, the Boston Edison Company, and the Consolidated Gas Electric Light and Power Company of Baltimore.

The author's thanks are due to Mr. S. R. Keyes, of the Boston Edison Company, and to Dr. Frank W. Chandler at the Polytechnic Institute of Brooklyn for many valuable suggestions. To Professor Robert Spice and to the late Professor William A. Anthony the author is especially indebted for assistance and inspiration afforded to him in his student days by their experimental lectures. It is to them that he owes his realization of the importance of such lectures in practical education.

Sydney Whitmore Ashe.

Brooklyn, N.Y., May, 1 910.

CHAPTER I Magnetism

Lodestone. Magnet. Earth as a Magnet. Horseshoe Magnet. Molecular Theory of Magnetism. Magnetic Induction. Effect of Temperature upon Magnetizability. The Effect of Vibration upon Magnetizability. The Obtaining of a Hysteresis Cycle. How to plot the Hysteresis Curve. Magnetic Field. A Magnet Pole travels along Lines of Force. Mayer's Needles. Practical Applications of Permanent Magnets. Ammeters, Voltmeters, Relays, Thomson Recording Wattmeters, Telephone Receivers. Questions . . 1-24

CHAPTER II Electro-magnetism

The Magnetic Field around a Straight Wire carrying a Current. The Compass Needle always tends to set itself Parallel to the Lines of Force. Effect of Current in a Coiled Wire. A Large Coil for Experimental Purposes. Limit Switch, Overload Relays. The Electro-dynamometer. Permeability, Saturation of Iron. The Electro-magnet. The Blow-out Magnet. Applications of Electro-magnetism. Electric Bells, Buzzers, Relays, Sounders. The Electric Motor. Thomson Inclined Coil Ammeters and Voltmeters. Thomson Inclined Coil Wattmeter. Weston Indicating Wattmeter. Traction Electro-magnets. Questions 25-45

CHAPTER III Electro-magnetic Induction — Theory of the Dynamo

Faraday's Discovery. Relation of Turns, Flux, Speed of Coil to E. M. F. Generated. Generators. Motor Generators, Double Current Generators, Rotary Converters, Balances. Variation of E. M. F. of viii TABLE OF CONTENTS

Generator. Magnetization Curve of a Shunt Dynamo. Residual Magnetism. Mutual Induction. Foucault or Eddy Currents. Applications of Foucault Currents. Practical Applications of Induction. Rumkorff Coil, Telephone Circuit, Wireless Circuit. Wireless Sending and Receiving Apparatus. Questions . . 46-58

Chapter IV

Electro-motive force, Current, Resistance. Resistance Defined. Ohmicvalues of Resistance. Circular Mil. Resistance of Copper Conductors. Temperature Coefficient. Wire Table. Electro-motive Force Defined. Standard Cells. Carhart-Clark Cell. Weston Cell. Current Defined. Values of Current. Ohm's Law. Applications of Ohm's Law. Example. Questions. . . . 59-76

CHAPTER V Primary and Storage Batteries

The Simple Cell. Galvani's Experiment. Chemical Action of Cell. E. M. F.'s of Cell. Effect of Changing Electrolytes. Polarization. Effect of Changing Electrodes. Depolarizers. Electrolytic Depolarizers. Electrolytic Condensers. Closed Circuit Cells. Daniell Cell. Local Action. Gravity Cell. Plating of Copper. Bunsen and Grove Cells. Grenet Cell. Open Circuit Cells. Leclanche Cell. Dry Cells. The Storage Battery. Theory of the Storage Battery. Operation of a Storage Battery. Rating of Cells. How to charge a Storage Battery. Edison Cell. Types of Commercial Cells. Questions 77-100

CHAPTER VI Electrolysis

Electrolytic Corrosion. Definition of an Electrolyte. Positive and Negative Temperature Coefficients. Decomposition of Acid Solutions. Electro-chemical Equivalents. Hoffman Voltameter. Electro-chemical Equivalent of Hydrogen. Polarity Indicator. Metallic Salt Solution. Electroplating. Copper Plating. Gold Plating. Silver Plating. Nickel Plating. Brass-plating Solution.

TABLE OF CONTENTS ix

Plating E. M. F.'s. Critical Current Density. Electrolytic Products. Alkalies and Bleach. Sodium. Aluminium. Potassium Chlorate. Sponge Lead. The Electric Furnace and its Products. Graphite. Calcium Carbide. Carborundum. Barium Hydrate. Miscellaneous Substances. The Electrolytic Rectifier. Electrolytic Interrupter. The Pail Forge. Questions ..... 101-118

CHAPTER VII The Three-wire System

Two-wire System. Three-wire Edison System. Three-wire System with Generator. Three-wire System Converter. Theory of the Three-wire System. Experiment on Three-wire System. Old and New Style Branch Circuits. Questions ...... 1 19-124

CHAPTER VIII Electrical Measurements

Ammeter and Voltmeter Method of Measuring Resistance. Measuring Resistance of Voltmeter. Voltmeter Method of Measuring Resistances. Comparison of Resistances with Voltmeter. Calibration of an Ammeter. Lamp Boards. Calibration of Ammeters. Series Method. Calibrating Rotary Ammeter. Calibrating Feeder Ammeter. Calibration of a Voltmeter. Potentiometer Method of Calibrating a Voltmeter. Calibration of an Indicating Wattmeter. Wheatstone Bridge Method of Measuring Resistance. Post-office Box. Slide Wire Bridge. Wire Roller Bridge. Resistance of an Electrolyte. Carey-Foster Bridge. Thomson Double Bridge. Insulation Test. The Galvanometer. How to set up a Galvanometer. Determination of Resistance of Galvanometer. Determination of the Constant of a Galvanometer. Measurement of Capacity. Com mercial Testing Sets. Questions 1 25-1 51

CHAPTER IX The Shunt Motor

The Shunt Motor. Testing out Circuits. Measuring Armature and Field Resistance. Magnetic Circuit of Field Coils. Tests for Improper Connection of Field Coils. Magnetic Circuits of Armature.

TABLE OF CONTENTS

Magnetic Circuits of Armature and Field. Neutral Plane. Changing Direction of Rotation. Operating Connections. Armature Circuit. Counter Electro-motive Force. Starting Boxes. Directions for Connecting up a Shunt Motor. Magnet Arm on Starting Box. Overload Release. Changing Direction of Rotation. Speed Variation. Rheostats. How to tell v^hether Field Resistance is All In or All Out. Theory of Speed Variation. Location of Trouble. Tests for Grounds. Tests for Short Circuits. Resistance of Ground. Interpole Motors. Questions 152-173

Chapter X

Characteristics of the Series Motor. Magnetic Circuits of the Series Motor. Resistance of Armature and Field Circuits of the Series Motor. Starting of a Series Motor. Speed and Tractive Effort Curves. Relation of Torque to Tractive Effort of Series Motor. Relation of Current Input, Speed, Torque, and Voltage of a Series Motor. Changing Direction of Rotation. Railway Controllers. Tw^o and Four Motor Equipments. Bridge Control. Multiple Unit Control. Emergency Brake of the Series Motor. Testing out Controller. Structural Features of Motor. Questions. . 174-185

Chapter XI

The Carbon Arc. Spectrum of Arc. Physics of Carbon Arc. Intrinsic Brightness of lUuminants. Efficiency of Light-giving Bodies. The Ultra Rays. Arc Lamp Circuits. Alternating Arc Circuit. Inclosed Arcs. Recent Developments in Arc Lamps. Factors to be considered in Selecting an Illuminant. Holophane Reflectors. The Flaming Arc. The Magnetic Arc. Questions . . 186-201

CHAPTER XII Incandescent lUuminants

The Carbon Incandescent Lamp. Early Discoverers. Edison's First Lamp. Making the Carbon Filament. Treating the Filament. Mounting the Filament. Characteristics of Filaments. The Tan-

TABLE OF CONTENTS xi talum Lamp. The Tungsten Lamp. The Tungsten Filament. The Moore Vacuum Tube. Feeder Valve for Moore Tube. The Cooper-Hewitt Mercury Vapor Lamp. The Nernst Lamp. Questions 202-220

CHAPTER Xni

Old Edison Bottle Meter. Thomson Recording Wattmeter. Armature, Armature Resistance, Compensating Coil, Field Coils, Magnets, and Gears of Thomson Recording Wattmeter. Type C Thomson Recording Wattmeter. Friction of Recording Wattmeter. Testing Meters. The Direct Method of Testing. The Rotating Standard Method. The Standardized Resistance Method. Load Box of Boston Edison Company. Installation Tests. Inspection Tests. How to make Tests. Method of Determining Normal Load. Modern Meter Installations. Meter Wiring. Questions . . 221-241

CHAPTER XIV Elementary Principles of Alternating Currents

Definition of an Alternating Current. Comparison with Direct Current. Instantaneous Current Curve. Sine Curve. Generation of E. M. F.'s. The Contact Maker. Balance Set to obtain E. M. F.'s. Method of Balancing E. M. F.'s. Oscillograph. Effective Current Values. Form Factor. Alternating Current Generators, Various Types. Capacity. Effect of Capacity in an Alternating Current Circuit. Capacity and Current Relation. .Capacity Reactance. Series Parallel Combination of Condensers. Self-induction. Derivation of Capacity and Self-induction Formulae. Relations of Resistance and Inductive E. M. F.'s. Relation by Means of Vectors of Resistance and Inductive E. M. F.'s. Vectors. Vector Relations in Single and Three-phase Circuits. Trigonometric Expressions. Meaning of Sines, Cosines, Tangents. Values of Sines, Cosines, Tangents. Circuits containing Resistance, Inductance, Capacity. Mathematical Relation of Inductance, Resistance, and Capacity. Series and Multiple Circuits. Reactance and Admittance Defined. Power in a Single-phase Circuit. Power Factor. Determination of Power Factor. Power Measurements in a Three-phase Circuit.

xii TABLE OF CONTENTS

Tangent Formulae. Single-phase Induction Wattmeters. Polyphase Integrating Wattmeter. Three-phase Circuit Current Lagging 30°. Questions . . . , 242-282

CHAPTER XV The Alternating Current Transformer

Theory of the Transformer. Relation of Transformer E. M. F.'s. Relation of Instantaneous E. M. F.'s. Operation of Transformer. Efficiency and Losses of a 400-kw. and an 800-kw. Transformer. Construction of a Modern Transformer. Experiments on Transformers. Types of Transformers. Manhole Transformers. Station Transformers. Six-phase Connections. Ratio of Transformers. Questions 283-298

CHAPTER XVI The Induction Motor

Theory. Windings. Slip. Experiments showing Poles, Transformer Features, Rotating Field, etc. Operation of an Induction Motor. Starting. Changing Direction of Rotation. Care of Induction Motors. Questions 299-306

Chapter XVII

Theory of E. M. F. Relations, Methods of Starting. Starting from Direct Current Side. Starting by Means of Induction Motor. Starting from Alternating Current Side. The Hunting of a Rotary Converter. Synchronizing. Synchronizing with a Voltmeter. Synchronizing with a Frequency Changer. Crossed Phases. Meaning of Unity Power Factor. Converters operating in Parallel. Recent Developments in Converters. The Booster Converter. The Interpole Converter, Rotary Converters versus Motor Generators, Questions 307-327

Experimental Projecting Apparatus 329-341

Formulae . 342

LIST OF ILLUSTRATIONS

I, 2, 3. Magnetic Spectrum. Compass. Repulsion of Magnets . . 2

4, 5. Attraction of Magnets. North Magnetic Pole .... 3

6. Magnetic Pole . . . . 4

7. Horseshoe Magnet from Weston Voltmeter . . . . . 5

8. Molecular Magnets 6

9. 10. Magnets made by breaking Magnetized Needle. Magnetic In-

11. Magnetization Loss with Heat 8

12. Keeper and Magnet . 9

13. Set-up for obtaining Hysteresis Curve II

14. Hysteresis Curve 12

15. Partial Hysteresis Curve 13

16. 17, 18, 19. Magnetic Spectrum. Shaker for Filings. Path of Lines

of Force. Cross Magnetization 14

20 a. Set-up show^ing that Magnet Pole travels along Lines of Force . 15 20b, 21. Small Electro-magnet. Molecular Magnets . . . .16 22, 23, 24. Movement of Weston Standard Voltmeter. Weston Standard Voltmeter Complete. Station Type of Weston Voltmeter . 17 25, 26, 27. Laboratory Standard Weston Voltmeter. Weston Station

Type of Ammeter. Magnets of Thomson Recording Wattmeter . 18

28. Thomson Recording Wattmeter 19

29, 30. Telephone Receiver (M. E. S. Co.). Weston Speed Tacho-

meter 20

31, 32. Weston Relay. Wattmeter Disc .21

33. Weston Ammeter, Central Zero, with Shunt 22

34, 35, 36. Magnetic Field around Wire. Presence of Field shown with

Filings. Field shown with Compass ...... 25

37, 38. Support for Compass for Projection. Neutralization of Magnetic

Field 26

39, 40. Wire carrying Current tends to encircle Magnet. Helix . . 27

41, 42. Solenoid (termed Long Tom). Sucking Coil .... 28

43. Limit Switch (Westinghouse) . . ... . . 29

44. Electro-dynamometer 30

xiii xiv LIST OF ILLUSTRATIONS

45, 46. Magnetization Curve. Filings showing Strength of Electro-magnet 32

47, 48, 49, 50. Nails showing Distribution of Flux of Magnet. Diaphragm and Magnet. Tracing the Field. Principle of Edison

Ore Separator • • ZZ

51, 52, 53. Arc extinguished with Magnet. Arc extinguished with

Electro-magnet. Electric Bell (M. E. S. Co.) .... 34

54, 55, 56, 57. House Bell Circuit (M. E. S. Co.). Circuit of Electric

Bell. Telegraph Line. Transmission Key (M. E. S. Co.) . . 35

58,59,60. Relays (M. E. S. Co.). Sounder. Eectric Motor . . 36

61, 62. Armature of Motor (Westinghouse). Field Coils of Motor

(Westinghouse) 37

63. Induction Motor (G. E. Co.) 38

64, 65, 66. Commutator (Westinghouse). Series Winding. Rotation

of Armature 39

67, 68, 69, 70. Shunt Connection. Series Connection. Armature and

Field Symbols. Cross-section of Armature (Westinghouse) . 40 71, 72. Thomson Inclined Coil Ammeters (Section). Thomson Inclined Coil Ammeter 41

73. Weston Wattmeter Movement ....... 42

74. Tractive Magnet built by Cutler Hammer Clutch Co. ... 43

75. 76, 77. Method of Generating Zero E. M. F. Lines of Force not

Interlinked. Generating an E. M. F. (Magnet and Coil) . , 46

78. Generating an E. M. F. (Coil and Coil) 47

79. Rotary Converter (G. E. Co.) 48

80. Motor Generator (Westinghouse) . 49

81. 82. Motor Generator (G. E. Co.). Circuit of Motor Generator . 50 83,84. Circuit of Balances. Field Circuit of Generator . . -51 85, 86. Magnetization Curve. Excitation of Generator ... 52

87. Principle of Induction 53

88. Wattmeter Disc with Magnets 54

89. 90. Principle of Eddy Currents. Insulation of Eddy Currents . 55 91, 92, 93, 94. Ruhmkorff Coil. Shocking Coil. Telephone Circuit.

Wireless Circuit . . . 56

95, 96. Wireless Sending Apparatus. Wireless Receiving Apparatus . 57

97. Desk Telephone 5^

98. Car Resistance .60

99. Circular Mil 61

100,101. Principle of Distribution of Potential. Carhart-Clark Cell . 66 \02a,\oib. Weston Cell. Weston Cell (Interior View) . . 67-68

103. Ohm's Law Illustrated 72

LIST OF ILLUSTRATIONS XV

104. Method of obtaining Low Voltage 75

105, 106. Galvani's Experiment. Voltaic Cell 77

107. Projecting Tank 78

108, 109. Support for Electrodes. Support in Position ... 79

1 10. Polarization Tank 80

111. Carbon Cell 81

112,113. Electrolytic Condenser. Electrolytic Cells in Series . . 82

114,115,116. Gravity Cell. Copper Electrode. Crowfoot Zinc . . 85

117. Plating of Copper 86

118,119. Leclanche Cell. Zinc for Leclanche Cell .... 87

120,121. Mesco Dry Cell. Red Seal Dry Cell 88

122. Variation of Resistance of H2SO4 90

123, 124. High Resistance of Pure Water. Conductivity of Pb02 and

PbS04 Shown 91

125. Battery Pellet 92

126, 127, 128. Battery Discharge Curve. Testing Sulphated Plate.

End Cells 93

129, 13c, 131. Battery Charging Circuit. Test Hydrometer. Charging

132. Charging Circuit 95

133, 134. Tudor Plates. Laboratory Chloride Cell .... 96 135, 136. Telephone Chloride Cell. Box Negative .... 97

137, 138. Exide Battery. Manchester Positive 98

139, 140. Rolled Negative. Shelf Negative 99

141, 142, 143. Conductivity of Sodium Acetate with Heat. Positive

Temperature Coefficient. Negative Temperature Coefficient . 102 144, 145. Electrolysis Projecting Tank. Decomposition of Acid Solutions ............ 104

146, 147. Hoffman Voltameter. Electro-chemical Equivalent of Hydrogen 105

150. Critical Current Density Apparatus iii

151. Wehnelt Interrupter 117

152. The Pail Forge ii8

153. 154, 155. Two-wire System. Edison Three-wire System. Three-

wire System (Generator) 119

156, 157, 158, 159, 160. Three-wire System (Converter). Principle of

Three-wire System . 1 20-12 1

161. Experiment on Three-wire System 123

162, 163. Old Style Branch Circuits. Approved Branch Circuits . .124 164. Ammeter-voltmeter Method of Measuring Resistance . . .125 xvi LIST OF ILLUSTRATIONS

165,166,167. Measurement of Resistance of Voltmeter. Weston Voltmeter Circuit (Station Instrument). Weston Voltmeter Suspension 127

168. Measuring Resistance with Voltmeter 128

169,170. Showing Distribution of Potential. Standard Resistance . 129 171, 172, 173, 174. Method of Connecting Contacts. Potential Taps.

Lamp Board . . 130

175, 176. Calibrating Rotary Ammeter. Calibrating Feeder Ammeter . 131 177, 178. Calibrating Ammeters in Laboratory. Calibrating a Voltmeter ... 132

179, 180. Leeds and Northrup Company Potentiometer. Circuits of

Leeds and Northrup Company Potentiometer . . . -133

181,182. Diagram of Potentiometer Circuit. Standard Cell Circuit . 134

183. Indicating Wattmeter Circuit . . . . . . .136

184, 185, 186, 187, 188, 189, 190. Calibration of Indicating Wattmeter.

Principle of Wheatstone Bridge ^Zl''^!)^

191. Post-office Box 139

192, 193. Galvanometer Shunt. Various Arrangements of Four-series

Resistances . 140

194. Slide Wire Bridge 141

195 a, 195 b, 196. Wire Roller Bridge 142

197, 198. Resistance of Electrolyte. Carey-Foster Bridge . . . 143

199. Insulation Test . . 145

200. Galvanometer 146

201. Measuring Resistance of Galvanometer 147

202. 203. Method of obtaining Low Potential. Low Potenial Obtained 148 204, 205. Measurement of Capacity. Substituting Switch . . . 149 206, 207, 208, 209, 210. Queen Slide Wire Bridge. Queen Acme Testing Set. Queen Decade Testing Set. Queen Laboratory Wheatstone Bridge, Queen Wheatstone Bridge . . . . .150

211. CQ. Motor installed on Ceihng . . . . : . .152

212. Testing out Circuits of Motor •. 153

213. Shunt Machine 154

214. 215, 216. Magnetic Circuits of Motor. Testing out Magnetic Cir-

217. Magnetic Circuits of Armature 156

218, 219. Changing Direction of Rotation. Measuring Field Current . 157

220. To show Induction of Field Winding 158

221. Starting of Shunt Motor 159

222. Starting Box 160

223. Starting Box Full On . . . 161

LIST OF ILLUSTRATIONS xvii

224. Starting Box (Westinghouse) . . ' 162

225. Cutler Hammer Starting Box ....... 163

226. Motor Circuits 164

227. 228. Field Circuit. Remote Control Resistance .... 165

229. Self-contained Rheostat (G. E. Co.) 166

230,231,232,233,234. Dial of Rheostat. Circuits of Rheostat. Field

Rheostat. Cross-section of Cutler Hammer Rheostat. Burnt out

Rheostat 167

235. Test for Grounded Armature . . , . . . .169

236, 237, 238. Test for Grounded Field Coil. Test for Short-circuited

Field Coils. Test for Short-circuited Armature Coils . . .170

239. Test of Grounded Switchboard . . . . . . • 171

240. Interpole Motor (G. E. Co.) 172

241. Series Motor Circuit 174

242. Measuring Resistances of Series Motor 175

243. 244. Tractive Effort of Series Motor. Relation of Torque to Trac-

tive Effort of Series Motor 177

245. Characteristic Curves of Series Motor 178

246, 247. Measuring Torque of Series Motor. Measuring Speed of

Series Motor . . 179

248, 249. Showing Relation of Speed to Current. Circuits for Changing

Direction of Rotation of Series Motor 180

250, 251, 252. Two Motors in Series. Two Motors in Parallel. Four

Motors in Series .......... 181

253, 254, 255. Four-motor Equipment. Four Motors in Parallel. Bridge

Control 182

256. Alternating Current Arc 186

257. Method of obtaining Spectrum 187

258. Temperature shown with Thermo Element 190

261, 262. Simple Arc Circuit. G. E. Arc Mechanism .... 193

263. Both Carbons Down-feed 196

264. Holophane Reflector . . 198

265. Carbon Incandescent Lamp 202

266. Squirting Filaments (Westinghouse Lamp Works) . . . 204

267. Drying Filaments (Westinghouse Lamp Works) .... '205

268. Bulb with Tip Added 207

269. 270. Filament Mount. Bulb ready for Exhaust .... 208

271. Tantalum Lamp 209

272, 273. Tantalum Filament. Circuit illustrating Positive and Nega-

tive Temperature Coefficient 210 xviii LIST OF ILLUSTRATIONS

274. Circuit to show Variation in Candle Power with Pressure . .211

276. Moore Tube 214

277. Feeder Valve for Moore Tube 215

278. Cooper-Hewitt Tube 216

279. Circuits of Cooper-Hewitt Tube 217

280. Westinghouse Xernst Lamp 218

281. 282. Glower. Circuits for Xernst Lamp . . . . .219

284, 285. Armature Resistance, T. R. W. Compensating Coil . . 222 286, 287, 288, 289. Field Coil, T. R. W. Magnets, T)i)e C Meter.

291. Parts of Type C, T. R. \V 224

293. Cover of Old Style T. R. W 226

294. 295. Wattmeter Circuit . 227

296. Friction Curves of Meters ........ 228

297. Calibrating a Meter 229

298. Standardized Resistance used by the Boston Edison Co. . . 231

299. Load Box, Boston Edison Co. 232

300. Service Test of Meter 233

301. Field Coils of Meter improperly Connected 234

302. Typical Meter Installation, Alternating Current Service . . . 236

303. 304. Typical Service of Meters. Combination Direct Current and

Alternating Current Service ....... 237

305. T. R. W. and T\'pe C Meter Service 238

306, 307. Typical Direct Current Service. Single A. C. Service . . 239

308. Typical Meter Installation 240

309. Instantaneous Current Curve . 243

310,311,312. Sine Curve. Generation of E. M, F 244

313, 314. Contact Maker 245

315, 316. Using a Balance Set to obtain E. M. F. Curve. Method of

Balancing E. M. F.'s 246

317. Balance Apparatus 248

318. Interior of Weston Alternating Current Voltmeter . . .251

319. 320, 321, 322. Single-phase Generator. Three-phase E. M. F.'s.

Three-phase Generator. Inductor Generator .... 253 323, 324. Experiment showing Charging of Cables. Dialectric Polarization ....... 254

325. Experiment showing Charging of Condensers with Direct Current . 255

LIST OF ILLUSTRATIONS xix

326. Capacity and Current Relations 256

327, 328. Relation of Sides in Right Angle Triangle. Condensers in

Series 258

329. Condensers in Parallel 259

330. Relation of Resistance and Inductive E. M. F.s . . . . 263

331. 332, 333. Line E. M. F. and Counter E. M. F. Resistance and In-

ductive E. M. F.'s. Alternating Current E. M. F. Curve . . 264

334. Relation of Current and Inductive E. M. F.'s .... 265

335, 336. Vector. Vector Relation of Inductance and Current . . 266 337> ZZ^i 339j 340- E. M. F. and Current in Phase. Vector Relation of

Current and Capacity Reactance. Y-connection for Three-phase Circuit. Relation of Transformer E. M. F.'s .... 267 341, 342. Resistance alone in Circuit. Vector Relation of Resistance

and Inductance 268

343. Trigonometric Relations in a Right Triangle .... 269

344, 345, 346, 347. Vector Relation of E. M. F.'s. Effect opposite to

Fig. 345. Ohmic Relation of Resistance and Reactance . .271 348, 349, 350. Parallel Arrangement of Reactances. Vector Relation

Admittance. Power in a Single-phase Circuit .... 273

. 274

351. E. M. F. and Current in Phase ....

352, 353. E. M. F. and Current out of Phase. Unity Power Factor . 275

. 276

• 277

. . 278

354. Experimental Method of Measuring Power Factor

355. Power Measurement in a Three-phase Circuit

356. 357. G. E. Single-phase Induction Wattmeter 358, 359, 360. Jewel Support of Wattmeter. Induction Wattmeter

Vector Relation of Single-phase Meter E. M. F.'s 361, 362. Vector Relation of Current and Potential Vectors in a Polyphase Meter. Polyphase Meter Vectors, Current Lagging 30^ . 281

363. Experimental Study of Transformer ...... 283

364, 365. Simple Transformer. Relation of Transformer Vectors . . 284 366, 367, 368. Relation of Instantaneous E. M. F.'s in a Transformer.

Load connected to Transformer. Load connected to I : I Transformer ............ 285

369. Modern Method of Building Transformers . . . . .287

370, 371, 372. Cross-section of Fig. 369. Queen & Co, Experimental

Transformer. Showing Principle of Transformer . . . 288 373» 374j 375j 376. Reluctance of Transformer Air Gap Shown. Study of Transformer. Varying Reluctance of Transformer. Measuring

Copper Loss of Transformer 289

377j 378* 379- Efficiency of Transformer. Manhole Transformer. Manhole with Transformer Installed 290

XX LIST OF ILLUSTRATIONS

380. Waterproof Terminals for Subway Transformer . . . .291

381, 382. Station Transformer Connections, Six-phase . . . 292-293 383, 384. Type H Transformers i : 2 Ratio. Type H Transformer i : \

Ratio 296

385, 386, 387. Ratios of Transformers. Neutralizing Self-induction of

Transformer. Transformer Secondaries in Series . . . 297

388. Transformer Secondaries connected in Opposition . . . 298

389. Induction Motor 299

390. Experimental Study of Induction Motor ..... 300

391. 392, 393. Copper Sphere. Transformer Feature of Induction

Motor Shown. Poles of Induction Motor Shown , . . 301 394, 395. Progression of Poles of Induction Motor with Current. Two-phase Induction Motor 302

396. Three-phase Induction Motor operated from Single-phase Circuit 303

397. Induction Motor operating a Blower ...... 304

398. Converter Armature 308

399. Synchronizing with Lamps 315

400. Synchronizing with Lamp connected to Transformers . . .316

401. 402. Synchronizing Two Converters. E. M. F. Relations when

Machines are out of Phase . . . . . . .318

403, 404. Crossed Phases. Unity Power Factor of Converters . .319

405. Experiment illustrating Unity Power Factor 320

409, 410, 41 1. Position of Zero Boost on Converter. Boost in a Positive

Direction. Boost in a Negative Direction 324

412, 413. Interpole Converter 325-326

414. Experimental Lantern arranged for Horizontal Projection . . 330

415, 416. Experimental Lantern arranged for Vertical Projection. Sin-

gle Lantern 331

417. Lantern Set-up 333

418. Two Lamps in Series 335

419. Automatic Arc Lamps . . . ZZl

420. Combination Beseler Double Lantern and Moving Picture Ap-

paratus 338

421. 422. Weston Projecting Instruments. Combination Board used

with Projecting Galvanometer 340

Chapter I Magnetism

Lodestone. — Lodestone is an oxide of iron, magnetitey FcgO^, which has the property of attracting small particles of iron and, when freely suspended, of assuming a position pointing north and south. It also has the characteristic of imparting its properties to a piece of steel that has been rubbed by it. It is quite heavy, of a black lead color, of considerable hardness, and is usually found in iron mines in various parts of the world. The name *' magnet" as applied to the lodestone, leading stone, not load stone, is derived through the Latin magnes or the Greek /j,ciyv7]^, meaning magnet. It is supposed that the Chinese used small pieces of this stone suspended as compasses two thousand years before the Christian era. A description of a primitive form of compass in use on the Syrian coast was given by Kibdjaki in 1242 a.d. In 1260, on the return of Marco Polo from Cathay, he brought a knowledge of the compass as used by the Chinese. The Italians give to Flavio Gioja the credit of inventing the compass in 1 300-1 320, but it is probable that he simply improved upon the old form of the instrument.

Magnet. — If a piece of steel is placed in a coil of wire carrying an electric current, it becomes magnetized. This magnetic condition of the steel may be observed by

Fig. I. — Magnetic Spectrum.

placing over the steel a piece of paper and sprinkling it with iron filings, thus obtaining a 7nagiietic spectrum.

In observing this spectrum it will be noted that the attraction of the magnet for the filings is greatest at both extremities of the magnet, the poles, and that it is practically zero at the middle of the magnet.

Now, if we substitute for the paper a piece of thin glass. Fig. i, and repeat the experiment, we shall note that the power of the magnet to attract the filings still exists. This fact leads to the conclusion that —

Magnetism cannot be Insjilated.

Experiment i . Place a piece of paper over a magnet and obtain a spectrum. Note that the lines of the spectrum seem to pass out from one pole and enter the other pole as though this imaginary force traveled in curves.

If a small magnet be pivoted, Fig. 2, so that it is free

to move, it will assume a definite direction

pointing north and south. When a magnet

is thus mounted, it is termed a compass.

Bringing another magnet near a compass

needle so that the north pole of the magnet is near the north pole of the compass,

Fig. 3, a repulsion of the end of the compass

needle occurs. The same effect will be noted if two south poles are brought near each other. If, however, a north pole and a soutJi pole be brought near each other. Fig. 4, attraction of the compass needle

Fig. 2. — Compass.

Fig. 3. — Repulsion Magnets.

occurs.

Like poles repel each other, and unlike poles attract each other.

Experiment 2. Bring near a compass needle first the north pole of a magnet and then the south pole, noting the result. Bring one end of a non-magnetized n!^^^'^,^

piece of iron near first the north and then the _JX,^^V-^

south pole of a compass needle, and note that ^^^v/\^

the piece of iron attracts both ends. Also ^^fc^

note that either end of the iron rod has the ^

same effect on the magnet. Why?

Earth as a Magnet. — A compass ^^

needle assumes the position pointing fig. 4. — Attraction of north and south because the earth Magnets,

possesses the property of a magnet, having a magnetic north and a magnetic south pole. The north magnetic pole is at some distance from the axial North Pole. The magnetic pole of the earth nearest the North Pole is termed the North Magnetic Pole, Fig. 5. A compass needle

points its north-seek- NORTH MAGNETIC/ \^ X ing polc in the direc-

tion of the north

^EQUATOR

magnetic pole. This is in reality a south pole; but as it seeks the north pole, we designate it as the north pole. This deviation of the magnetic pole from the axial pole becomes more and more marked as the

SOUTH POLE

Fig. 5. — North Magnetic Pole.

compass needle is located farther and farther north on the earth. As the compass needle approaches the north geographical pole of the earth, it is affected by the north magnetic pole in the same manner as it would be if it were approaching the pole of a magnet; thus it dips more and more. The north magnetic pole in the northern hemisphere of the earth is located at Boothia Felix, Fig. 6, at about latitude 70 and longitude 96 west.