Question

A polyphase induction motor of the slip ring or wound rotor type can be used ____________

(a) for high start-up torque applications

(b) as a frequency converter

(c) any of the mentioned

(d) none of the mentioned

This question was addressed to me by my college director while I was bunking the class.

This is a very interesting question from Generated EMF topic in portion Principles of Electro mechanical Energy Conversions of Electrical Machines

Answer 1

Correct answer is (c) any of the mentioned

Easy explanation: A polyphase induction motor can be used as a frequency converter (or changer) for changing the supply frequency f to other frequencies sf and (2-s)f at the slip ring terminals.