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 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. 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 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 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 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 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 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 |