DIRECT-CURRENT DYNAMOS AND MOTORS. 119 
— y) 
ii Ww Seg eat Me, ..(65) 
in which W = electrical power at terminals; that is, 
output of generator, or intake of 
motor; 
W’ = electrical power active in armature; 
W” = mechanical power at dynamo shaft; 
that is, driving power of generator, 
or mechanical output of rotor, re- 
spectively; 
W, = power absorbed by armature winding; 
We. = power used for field excitation; 
Ww, = power consumed by hysteresis; 
We = power consumed by eddy currents; 
w: = power loss due to air resistance, brush 
friction, journal friction, etc. ; 
W. = power required to run machine at nor- 
mal speed on open circuit; 
Wo = Wy + We + We. 
85. Formulas for Commercial Efficiency.—Substitut- 
Com. 
Com. 
Com. ED: = BOF Ort rn) + Cara Ot wo 
ing in the above formulas (64) and (65) the values of 
W, w,, and W,, the following formulas are obtained, in 
which the symbols employed have the same meaning as 
in formulas (58) to (63): 
Series-wound generator: 
E 
EO. = BOLO (r+ tu) + Wy FW we 
-++-(66) 
Shunt-wound generator: 
EC : 
Ef. = EC + Cure! + Can’ Pan” + Wn + We + We’ 
..)-(67) 
Compound-wound generator: 
HC 
(68) 
