ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 173 
and the resulting hysteresis and eddy current losses are 
4.150 watts. 
326. Total Armature Losses and Temperature Rise. 
—The total armature losses amount to 8,720 watts, for 
which the cooling surface is 9,050 square inches, composed 
. of the internal and external cylindrical surfaces and six 
side faces. 
According to Equation (40), the resulting temperature rise 
; 8,720 5 ua. 
is equal to T, = 75 X = 72° F., which is below the 
] 
specified temperature rise of 75° F., see Par. 299. 
32%. Full Load Efficiency.—In previous paragraphs, the 
following losses have been calculated, from which the 
efficiencies may be found. | 
Armature copper loss at inductive full load... .2,200 watts; 
Beene IF00 LOSSES... 0... ok en's viele eee GGR0 75°» -s 
the corresponding excitation energy........ ieee Ses 
and an allowance for the friction and ventila- 
NN IAN ois iho as evn 600% 2)3s0'i Caw wets aeuee sos 
MIE MATOUBL GE 15.5.5 bios 0 oe oes wc wey soe 15,700 watts. 
The full load efficiency, with the total loss of 15,700 watts, 
175,000 
is equal to = 92 per cent., which is 
175,000 + 15,700 
slightly higher than that specified, see Par. 299. 
328. Half Load Efficiency:.—With half load the iron and 
friction losses remain the same as on full load while the 
armature copper loss is equal to 550 watts and the excita- 
tion energy 2,450 watts; this latter value being obtained 
by simple interpolation between the maximum and mini- 
mum excitation losses. 
The half load efficiency, which is not of great importance, 
87,500 
$7,500 + 13 320 
is also satisfactory, being = 87 per cent. 
