Discussion in 'Homework Help' started by liutukas0725, Nov 21, 2012.

1. ### liutukas0725 Thread Starter New Member

Nov 21, 2012
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I am struggling with one of the question from coursework sheets, could you help me please?
A permanent magnet DC motor has an armature resistance of 0.5  and when a voltage of 120 V is applied o the motor it reaches a steady-state speed of rotation of 20 rev/s and draws 40 A. What will be (a) the power loss in the armature and (b) the power input to the motor?

Hopefully some one will give me a clue. I am not sure if the current given is the armature current or the real current of motor.

Many thanks

2. ### tshuck Well-Known Member

Oct 18, 2012
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It depends, what motor model are you using?

This may be of assistance...

3. ### liutukas0725 Thread Starter New Member

Nov 21, 2012
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Well it does not say in the question...might it be the problem for solving it?

4. ### kris.92 New Member

Nov 26, 2012
11
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the kind of motor doesnt matter if it says its a permanent magnet motor. (that is the motor). You have all the information in the question to answer it. I don't want to give you the answer, but just dont get caught up in the model of motor nonsense.

#12 likes this.
5. ### tshuck Well-Known Member

Oct 18, 2012
3,531
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Really? What equations do you apply then? This is highly dependent of the motor model used. A simple series resistance can be used, or a whole 2nd order system. The solution depends on the model.

6. ### #12 Expert

Nov 30, 2010
16,665
7,313
Think: What windings does a permanent magnet motor have besides the armature winding?

Oct 18, 2012
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675