ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 31 
CHARACTERISTIC DATA. 
58. Characteristic Data.—tThe basis for the calculations of 
any machine is formed by the designer on the standard 
characteristic data supplied to him, from which he provides 
a generator to deliver a certain current at a certain ter- 
minal voltage and frequency. 
The characteristic data of an alternator are as follows: 
The normal capacity in A.W. and in KVA. 
The normal working pressure on the line, in volts. 
The normal speed in revolutions per minute. 
The number of cycles per second or the alternations per 
minute. 
The number and connection of phases. 
Further, if not specified, the values of efficiencies must be 
decided upon and the permissible amount of inherent regu- 
lation is to be fixed. 
59. Kilo Watts, Kilo Volt Amperes and Horse 
. Power.—From the data of K.W. and KVA. the de- 
signer learns what capacity the prime mover must have 
and for what output the generator must be designed. Sup- 
posing that an alternator has to supply « K.W. to a power 
circuit of induction motors, and assuming the line load has 
a power factor of cos g,: then the generator must be 
capable of developing «x ewe =x KVA.; that is, the 
generator is to be rated for the normal output in KAVA. 
The size of the prime mover will be caleulated on the basis, 
that it has to cope with the specified K.W. on the line and 
with the additional losses in the generator. Therefore, if 
the generator efficiency on inductive full load is equal to 7, 
the capacity of the engine in horse power has to be equal 
|) ES gemapagemanacras 
nm X .746 
