I _' STA XDA RDIZA TION R VLES OF Til / ,17 



6 K \IIN-. i^ KII.OWAIIV KUvtncal power should be expressed in kilo- 

 watts, except when otherwise specif; 



67 : . ii "\ i i AMPERES. Apparent power in altrrnaiing- 

 currcnt uld be expressed in kilovoft-amperes as distinguished 

 from effective power in kilowatts. When the power factor is 100 per 

 cent, the apparent power in kilo volt -amperes is equal to the kilowa? 



68 The RATED (PULL- LOAD huh. with the rated 

 terminal voltage, gives the r.itr<l kilowatts, or the rated kilovolt-amperes. 

 In machines in which the rated voltage differs from the no-load voltage, 

 the rated etirretU should refer to the for 



9 DETERMINATION OF RATED CURRKM. The rated current may be de- 

 termined as follows: If P- rating in watts, or volt-amperes if the power 

 han 100 per cent, and full-load terminal voltage, 

 the rated current per terminal 

 p 



70 / = amperes, in a direct -current machine or single-phase alternator. 







1 P 



71 I m ' - i? amperes, in a three-phase alternator. 



\ 3 & 



\ P 



72 / = () amperes, in a quarter-phase alternator. 



73 NORMAL CONDITIONS. The rating of machines or apparatus should be 

 based upon certain normal conditions to be assumed as standard, or to be 

 specified. These conditions include voltage, current, power-factor, fre- 

 quency, wave shape and speed; or such of them as may apply in each par- 

 ticular case. Performance tests should be made under these standard 

 conditions unless otherwise specified. 



74 a. POWER FACTOR. Since the inherent capacity of alternating current 

 generators, synchronous motors, and transformers, depends upon their 

 voltage and their current, they should be rated in kilovolt-ampere^ If 

 the apparatus is rated in kilowatts without specification as to the power 

 factor, a power factor of 100 per cent shall be understood. 



If rated in kilowatts and a power factor other than 100 per cent be 

 specified, this should be understood as defining only the nature of the load, 

 and not as implying an increase in the ampere rating of the apparatus, which 

 should be based upon the kilowatt rating at 100 per cent power factor. 

 76 b. WAVE SHAPE. In determining the rating of alternating-current ma- 

 chines or apparatus, a sine wave shape of alternating current and voltage 

 is assumed, except where a distorted wave shape is inherent to the appar- 

 atus. See Sees. 79-80. 



76 FUSES. The rating of a fuse should be the maximum current which it 

 will continuously carry. 



77 CIRCUIT-BREA'KERS." The rating of a circuit-breaker should be th> 

 imum current which it is designed to carry continuously. 



77m NOTE. In addition thereto, the maximum current and voltage at 

 which a fuse or a circuit-breaker will open the circuit should be specified. 

 It is to be noted that the behavior of fuses and of circuit-breakers is much 

 influenced by the amount of electric power available on the circuit. 



78 I sim AUNG METERS should be rated according to their full-scale 

 reading of volts, amperes, or watts. In wattmeters the rated volts and 

 rated amperes should also be included; i.e., the volts and amperes which 

 can be safely and continuously carried by the voltage and current coils 

 respectively. 



78* WATT-HOUR METERS should be rated in volts and amperes. 



B. WAVE SHAPE. 



79 The SINE WAVE should be considered as standard, except where a de- 

 viation therefrom is inherent in the operation of the apparatus 



80 A MAXIMUM DEVIATION of the wave from sinusoidal shape not exceeding 

 10 per cent is permissible, except when otherwise specified. See Section 5j. 



81,82,83. See Sections 5e to 51. 



