Question

Two of the supply terminals to a three phase induction motor gets interchanges while regular scheduling work. When the machine is switched on, then it will _________

(a) rotate in opposite direction

(b) rotate in same direction

(c) not start

(d) get heated and winding will burn

The question was asked during an interview.

This intriguing question originated from Rotor EMF, Current and Power in portion Induction Machines of Electrical Machines

Answer 1

The correct answer is (a) rotate in opposite direction

To explain I would say: As the supply phase sequence is reversed, the machine’s developed emf will also be reversed.