shaunt dc motor

Thread Starter

qwerty321

Joined Oct 22, 2008
14
Hello, I have this small problem in which I need some help:

An 8- hp, 220- V, 3000- rpm shunt dc motor has a rated efficiency of 85% with a rated current of 0.3A in the shunt field winding. What is the armature resistance of this motor?
(0.819Ω is the answer but I don't know how to get it.

I am trying to relate the efficiecny to the losses which include (RF*IF+Ra*IA) but cannot get the result
Thank you for the help
 
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