Question on induction motor rotor copper losses

[scutzi128]

Homework Statement

The rotor of a 3 phase 60hz 8-pole induction motor takes 220w @ 3hz. Find the rotor speed and the rotor copper losses.

2. The attempt at a solution

I have found the rotor speed by using the equation slipspeed = fr(120)/P = 3hz(120)/8 = 45 rpm then finding nsync by 120(60)/8 = 900rpm so rotor speed = 900-45 = 855rpm. Slip can also be found to be 5% from this. I am stuck at trying to find the rotor copper losses though. I thought that it was just the 220w but that seems to easy. I would appreciate any help with this problem. Thank you.

 

[scutzi128]

Never mind I figured it out. It is slip*(input power to rotor) so .05*220w = 11w.