THE DESIGN OF ALTERNATING 
GENERATORS AND SYNCHRONOUS 
MOTORS. 
DESIGN OF A STANDARD SPEED, REVOLVING 
FIELD TYPE, THREE-~PHASE ALTERNATOR. 
299. General Specification of Alternator.—The gener- 
ator, direct coupled to a high speed steam engine, should 
be capable of delivering 175 KVA. to a power circuit with 
cos P = 0.85. 
- The terminal voltage on the star connected armature has 
to be 220 volts, with a frequency of 40 cycles per second. 
The voltage drop should not exceed 4% on a non-inductive 
full load with cos P =—1, and not exceed 12% on an 
inductive full load with cos P = 0.85. 
The efficiencies should not be less than 91% for inductive 
full load and 87% for inductive half load. 
The temperature rise on any part of the machine should not 
exceed 75 degrees Fahrenheit, provided that the tempera- 
ture of the surrounding air is 65 degrees Fahrenheit. 
300. Engine Speed.—The engine makers state that the ap- 
proximate highest speed they can run their engine of 
175 X 0 85 ; 
0.91% 0.746 ~ 220 H.P. (see Par. 59) is 400 R.P.M., 
which corresponds to a generator with 12 poles (see Equa- 
tion 7). 
301. Armature Stampings.—From Table 16, a diameter 
of about 45 inches would be a standard value, but as the 
next smaller size of stamping, 35.4 inches diameter, is in 
