ALTERNATING GENERATORS AND SYNCHRONOUS ‘MOTORS:. 23: 
47%. Temperature Rise.—The total cooling surfacé of the 
field coils is equal to O,=L, XdxX2p+2bxfx2p, which 
in the present case is equal to 5.75 x 38K16+-2 «4.75 
x 12 x 16=5350 sq.inches. The mean value of the speed is 
54 3.14375 _ 
12 
(41), the temperature rise will be equal to ory 
4680 x 100 
5350 (1--0.0002 x 5300) =42.5 degrees Fahrenheit. 
= 5300 feet per minute. From, Equation 
478. Armature Copper Loss.—The length of mean arma- 
_ ture winding is equal to L, = (1342.1 x 12.4) 2=7 
ZLy ss 
> SE (i 
32 13x78 
2x2~x 0.0201 
inches and by means of the Equation 3 X 
the ohmic resistance. works out as 3 X- 
g 
Sara 0.97 ohm. Therefore the armature copper loss 
on full load with cos p= 0.9 for the phase current, will be 
81° x 0.97=6,490 watts. 
479. Losses in Teeth.—The losses in the teeth art one part 
: of the armature iron losses, and with reference to Fig. 
29, and by means of equation Sx7x rxlx0.9x.28 
(wrtw.)= W,, it equals 850(4.2+-0.9) =4,340 watts. 
480. Losses in Core.—The weight of the armature core is 
equal to 4,500 lbs. and the losses therein are 4,500 (1+0.2) 
= 5,400 watts. 
481. Temperature Rise in Armature.—tThe total ar- 
mature losses will be 6,400+4,340+5,400=16,140 watts 
and the corresponding cooling surface, 2,400-+3,000+6 
x 1,900=16,800 sq. inches. Therefore, from Equation 
16140 
(40), a temperature rise of 7’, =75x 16800 
=72.5 degrees 
Fahrenheit is obtained. 
