Question

Plugging is applied in a motor, if we don’t make the switch OFF what will happen?

(a) Motor will come to rest as a result of plugging

(b) Motor will come to rest and will start rotating in another direction

(c) Motor will burn

(d) Nothing will happen

I have been asked this question in an interview.

Question is from Braking of DC Motors topic in division DC Motors of DC Machines

Answer 1

The correct choice is (b) Motor will come to rest and will start rotating in another direction

The best explanation: If the switch is kept ON near to zero speed, motor will have braking torque acting in opposite direction greater than the electromechanical torque. Thus, motor will come to rest and for the next instant motor will start rotating in opposite direction.