174 ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 
329. Summary of Design.—The regulation of the present 
alternator is better than the average of standard machines. 
The weights of the copper and armature stampings compare 
favorably with those of a corresponding standard gener- 
ator, while the weight of iron material is larger and that 
of copper considerably less. 
The output constant for the alternator in question is- found 
2 » 2 
equal to _ ees sal — ani 34 x 10° 
which points to a successful design, as regards economy 
in dimensions. 
DESIGN OF A 25-CYCLE REVOLVING FIELD TYPE 
.THREE-PHASE ALTERNATOR. 
330. General Specification of Alternator.—The 25-cycle 
300 KVA. three-phase generator, which has to supply a 
power circuit under a line pressure of 500 volts, shall fulfil 
the following, conditions : : 
The power factor of the circuit is assumed to be 0.8; the volt- 
age drop at full load shall not be more than 20 per eent.; 
the full load efficiency must be at least 93 per cent., and the 
temperature rise shall not exceed 75° F. 
331. Speed.—After consulting the engine makers, it has been 
decided to run the alternator at a speed of 375 revolutions 
per minute. The corresponding number of poles for that 
speed will be 8. 
332. Number of Slots.—With reference to Fig. 62, the most 
suitable flux will be found to be about 56 X 10°, the ratio. 
KVA. 
N 
. From Equation (35), the corresponding value of armature: 
ampere conductors is equal to 3 Z X C = 78,000. 
We will allow about 1,000 ampere conductors to be placed 
being equal to 0.8. 
