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3d. Induction motors: 25 per cent for one-half hour, 50 per cent for one minute.

4th. Synchronous converters: 50 per cent for one-half hour.

5th. Transformers: 25 per cent for one-half hour; except in transformers connected to apparatus for which a different overload is guaranteed, in which case the same guaranties shall apply for the transformers as for the apparatus connected thereto.

6th. Exciters of alternators and other synchronous machines, 10 per cent more overload than is required for the excitation of the synchronous machine at its guaranteed overload and for the same period of time.

APPENDIX I.
EFFICIENCY.

Efficiency of Phase-Displacing Apparatus. —

In apparatus producing phase displacement, as, for example, synchronous compensators, exciters of induction generators, reactive coils, condensers, olarization cells, etc., the efficiency should be understood to be the ratio of the volt-ampere activity to the volt-ampere activity plus power loss.

The efficiency may be calculated by determining the losses individually, adding to them the volt-ampere activity, and then dividing the volt-ampere activity by the sum.

1st. In synchronous compensators and exciters of induction generators, the determination of losses is the same as in other synchronous machines under Sections 10 and 11.

2d. In reactive coils the losses are molecular friction, eddy losses, and /Vloss. They should be measured by wattmeter. The efficiency of reactive coils should be determined with a sine wave of impressed E.M.F., except where expressly specified otherwise.

3d. In condensers, the losses are due to dielectric hysteresis and leakage, and should be determined by wattmeter with a sine wave of E.M.F.

4th. In polarization cells, the losses are those due to electric resistivity and a loss in the electrolyte of the nature of chemical hysteresis, and are usually very considerable. They depend upon the frequency, voltage, and temperature, and should be determined with a sine wave of impressed E.M.F., except where expressly specified otherwise.

APPENDIX II.

Apparent Efficiency.—

In apparatus in which a phase displacement is inherent to their operation, apparent efficiency should be understood as the ratio of net power output to volt-ampere input.

Such apparatus comprise induction motors, reactive synchronous converters, synchronous converters controlling the voltage of an alternating-current system, self-exciting synchronous motors, potential regulators, and open magnetic circuit transformers, etc.

Since the apparent efficiency of apparatus generating electric power depends upon the power factor of the load, the apparent efficiency, unless otherwise specified, should be referred to a load power-factor of unity.

APPENDIX III. Power Factor and Inductance Factor. —

The power factor in alternating circuits or apparatus may be defined as the ratio of the electric power, in watts, to volt-amperes.

The inductance factor is to be considered as the ratio of wattless voltamperes to total volt-amperes.

Thus, if p = power factor, q = inductance factor,

p1 + q1 = 1.

„, r . • ., (energy component of current or E.M.F.)

The power factor is the - 5^— ^ ., '

(total current or E.M.f.

and the inductance factor is the

(wattless component of current or E.M.F. — true power.

(total current or E.M.F., volt amperes.

Since the power-factor of apparatus supplying electric power depends upon the power-factor of the load, the power-factor of the load should be considered as unity, unless otherwise specified.

APPENDIX IV.

The following notation is recommended : —

E, e, voltage, E.M.F., potential difference.

/, /', current.

P, power.

*, magnetic flux.

<Sh magnetic density.

R, r, resistance.

X, x, reactance.

Z, z, impedance.

L, 1, inductance.

C, c, capacity.

Vector quantities when used should be denoted by capital italics.

APPENDIX V.

Table of Sparking Distances in Air between Opposed Sharp NeedlePoints, for Various Effective Sinusoidal Voltages, in inches and in centimeters.

[table]

INDEX.

PAGE

Admittance 127

Ageing of Transformer Iron 155

Alternating Currents 109

Fundamental Waves 112

Harmonic Waves 112

Circuits, Calculation of 224

Power of 119

Systems of Distribution 186

Wave, Form of 112

Aluminum as a Conductor 3, 238

Angle of Lag 117

Arc, the Electric 297

Lamps 3'29

Arc Lamp, Carbon of Direct Feed .... 346

Cut-outs 340

Composition of the Light 313

Clutches 346

Dash Pots 356

Differential Mechanism 339

Double Carbon 343

Focusing 342

Inverted 348

Magnetic Circuits in Mechanisms . . . 342
Mechanisms of Typical Lamps 336 to 351

Rod Feed 344

Shunt Mechanism 338

Arc Circuits, Incandescent Lamps on ... 24

Arc Lighting, Series 21

Brush System 22

Arc Light Globes 332

Arc, the Alternating 318

Inclosed 327

Appearance of 298

Carbons for 302, 329

Candle-Power of 308

Blowing-out of 314

On Constant Potential Circuits . . 315,325

Inclosed 320,323

Hissing of the 308

Efficiency of the 311

Resistance of the 306

Series Inclosed 323

Troubles that Occur in the 317

Short 314

Unstable 314

Watts Consumed by the 308

Volts and Amperes Required for the, 303, 312

Belknap Voltage Regulator 57

Boosters 99

Induction Type 206

Method of Feeder Regulation .... 67

Bus bars, Auxiliary 64

PAGR

Cables for Electric Lighting 281

Concentric 284

Callender System 280

Capacity 120

Of Cables and Conductors 136

Effect on Current 121

Formulas for 138

Means of Reducing 138

Cardew Earthing Device 176

Circuit-breakers 389

Chapman Voltage Regulator 57

Cleats 376

Compound Dynamos, Regulation by . . . 53

Composite Wound Alternator 193

Compensator for Voltmeter 199

Motor-Dynamo as 99

Compensated Field Alternator 195

Conductors, Current Capacity and Table . 13, 15
Design and Economy in ... 10, 87, 226

Measurement of 1

Materials for 3

Overhead 237

Underground 262

Conductivity of Copper 4

Coefficient of Change of Resistance .... 6

Copper Wire Table 8

Losses in Transformers 153

Conductors, Economy in . . . 10,87,226

Constant Potential Regulator 57

Current Transformer 176

Conduit, Cast Iron 267

Fiber 273

Earthenware 269-277

Pipe 263,207

Wooden 272.273

Edison Tube System 273, 279

Converter, Rotary 96

Cooling of Transformers 167

Core Losses in Transformers 154

Cross Arms 247

Crompton System 279

Cut-out, Thomson Film 170

Cut-out, Cabinet 392

Delta Connection, of Three-phase Circuits . 145

Direct-Current Transformer 97

Distribution, Electrical 1

Alternating Current Systems of . 186 to 223

From Underground Conduits 291

D. C. Transformers 93

Parallel Systems of 28

Polyphase Svstems of 200

Single-phase Systems of 186

TACE

Distribution, Scries Systems of 17

Dobrowolsky Three-wire System 77

Donshea Method of Field Excitation ... 00

I >ouble-Current Generator 215

Drop 9

On Mains, Calculation of 38

On Net Works 103

I)rawing-in of Conductors 288

I >ynamotor .93

Dynamo, Compound 53

Double 74

Economy in Conductors 10, 87,220

Edison Tube System 273

Eddy Current Losses 15G

Efficiency of Transformers 159, l0l

All Day.TabL- 1£5

Effective Value of A. C. Volts and Amperes . 114
Exciting Current in Transformers .... 125

Farad lao

Feeders .J84

Regulation t , 195

Flashing Filament; 197

Filaments of Incandescent I.,mips .... 395

Anchored 407

Resistance of 110

Sizes of Ill

Fished Wiring .»1

Five-wire Systems 86

Fixtures for I^imps 192

Flux Densities in Transformer Cores . . . 157

Frequency Changer 218

Frequency Ill

Choice of 224

Foucault Current Losses i66

Fuse Blocks for Transformers 179

Grounded Shield for Transformers . . .177

Grounding the neutral of 3-wire system . .

S4 and A pp. I

of Transformers .... 177 and App. I

Guard Wires and Hooks '-17

Guying Pole Lines 246

Harmonics in A. C. Waves 112

Henry 115

High Voltage D. C. Distribution 100

Holophane Globe 334

Hysteresis Loss in Transformers ..... 155

Impedance 131

of Parallel Circuits 126

Due to Resistance and Inductance . . . 116

of Series Circuits 126

Incandescent T-tmps 39.>

Incandescent Lamp Bases and Sockets 401

Globes 399

on Arc Circuits 24

Light Distribution 407

Target Diaenm 417

Voltage, Candle-Power, Efficiency and
Life 413

PACE

Inductance . , 114

Effects, Means of Reducing 332

Lag of Current due to 117

Table of 130

Induction Motor 147

Induction, Self and Mutual 115

Insulation 248

Interior Conduit 379

Wiring 374

Iron Losses in Transformers 154

Joints in Cables 285

in Line Wires 253

Kelvin's Law 11

Kennedy's System 280

Knob and Tube Wiling 378

Lag of Current 117

Lag Due to.Inductance . 117

Lead of Current 121

Leakage Current in Transformers .... 158
Leakage, Magnetic in Transformers .... 1£0
Lightning Arresters 176

Magnetizing Currents in Transformers . 158

Magnetic Leakage in Transformers .... 1C0

Mains, Calculation of ;i8

Mains and Taps £83

Manholes 286

Matthiessen's Standaid of Conductivity . . 6

Mershon Compensator 190

Mesh Connection. See Delta.

Meters ... 432-451

Motor-Converter S3

Motor-Dynamo . 93

Motor' Dynamos as Boosters ...... 99

as Compensators 99>

Motor, Induction 147

Synchronous . . 147

Transformer 93

Municipal Lighting Circuits 15

Mutual Induction • 15, 134

Inductance of Circuits 131

Naked Conductor Underground Systems . 279-

Networks of Conductors 103

Current and Drop in 103

Design of 106

Neutral Conductor, Grounding of , 84 and App. I

Over-Comuound dynamos, regulation by . 53

Overhead Conductors 237

Insulators for 248

Materials for 237

Poles for 243

Sag and Stress in 241

Specifications for 237

Psnel Board 392

Parallel Svstems of Distribution 28

Regulation of 5t

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