Question

What is the formula for the maximum value of current through end ring, when the current is not maximum in all the bars under one pole at the same time?

(a) maximum current in end ring= (2*3.14) / (bars per pole/2*no of poles) * current per bar

(b) maximum current in end ring= (2/3.14) * (bars per pole/2*no of poles) / current per bar

(c) maximum current in end ring= (2*3.14) * (bars per pole/2*no of poles) * current per bar

(d) maximum current in end ring= (2*3.14) / (bars per pole/2*no of poles) / current per bar

The question was asked in an online quiz.

My enquiry is from Design of End Rings topic in section Three Phase Induction Motor of Design of Electrical Machines

Answer 1

Right answer is (c) maximum current in end ring= (2*3.14) * (bars per pole/2*no of poles) * current per bar

Easy explanation: The bars per pole is first obtained. Then the no of poles is calculated along with the current per bar. On substituting in the formula the maximum current in the end ring with the current through all the bars under one pole is not maximum.