146 ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 
The total core loss will therefore be equal to 
4,300(0.95 + 0.225) = 5,050 watts. 
262. Total Loss in Armature.—tThe total amount of energy 
dissipated in the form of heat in the armature is equal to 
5,200 + 3,550 + 5,050 = 13,800 watts. 
263. Cooling Surface and Temperature Rise.—With 
reference to Par. 204, the available cooling surface in 
the present design is as follows: 
The external cylinder surface: 76 X 3.14 X 9.5 = 2,300 
square inches; 
the inner cylinder surface: 55 X 3.14 X 9.5 = 1,650 square 
inches ; 
: 76? — 55? 
the two outer side faces: 2 x RRS X 3.14 = 4,300 
square inches; 
and the two faces inside the ventilating duct = 4,300 
square inches; 
making a total cooling surface of 12,550 square inches. 
This gives 0.9 square inch per watt loss, and according to | 
Equation (40), the temperature rise will be: 
13.800 
12,550 ! 
The temperature rise is slightly high, and from all appear- 
ances, it would have been advisable to employ a second 
ventilating duct. | 
75 X ==-82°, FF, 
264. Total Losses in Alternator.—The various losses in 
the alternator under discussion are as follows: 
The friction and ventilation losses are on the basis of the 
data in Fig. 25 estimated at............... 7,000 watts; 
the iron losses have been calculated as....... 8,600 watts; 
the armature copper losses for a phase cur- 
rent of 66 amperes equal.......... ....9,200 watts; 
