144 
ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 
| 254. 
255. 
206. 
Temperature Rise of Field Coils.—The maximum 
energy utilized in the field coils will be 244.5? x 0.0865 
= 5,150 watts which will cause a temperature rise of about 
42°F, according to the following calculation based on the 
data in Par. 205. | 
The cooling surface of a coil is composed of the external 
eylindrical surface which is about 
; 6 X (11.6 + 8.6) x 2 = 242 square inches. 
The two iron sections, one next to the pole shoe, and the 
other next to the wheel rim, are equal to 2 X 6 xX 9= 108 
square inches. Therefore, the total cooling surface of 
all 12 coils is equal to 12 (242 +108) = 4,200 square 
inches. 
According to Equation (41) the temperature rise is equal 
to 
5,150 
4,200(1 + 0.0002 x 7,150) 
During the actual tests of this machine a temperature rise 
of 46°F. was recorded. 
85 X = 42° Ff. 
Length of Armature Winding.—The maximum 
energy utilized in the armature winding is found as 
follows: ; 
The length of mean turn equals 77 inches from actual meas- 
urement; or, if caleulated by means of Equation (12), 
T= 2(10+ 2 X 14.4) = 77.6 inches. 
The number of turns per phase being 12 x 18 = 216, the 
length of the turns which are connected in series will be 
77 X 216 = 16,632 inches, or, that of all three phases is 
equal to 49,896 inches. 7 
Weight of Armature Copper.—Each conductor con- 
sists of two parallel connected No. 9 S.W.G. wires, the 
effective section of which is equal to 2 x 0.01629 = .03258 
square inches; therefore the weight of armature copper 
is equal to 49,900 x 0.03258 x 0.32 = 520 pounds. 
