Question

Why starters are required in a DC motor?

(a) Back emf of these motors is zero initially

(b) These motors are not self-starting

(c) These motors have high starting torque

(d) To restrict armature current as there is no back emf at starting

I had been asked this question in class test.

The question is from Starting of DC Motors topic in section DC Motors of DC Machines

Answer 1

The correct option is (d) To restrict armature current as there is no back emf at starting

The best I can explain: At the time of starting (n=0), the induced emf of a motor is zero such that current drawn by armature, from rated voltage supply would be Ia= V/Ra. Since armature resistance is very low, armature current drawn is very high and will damage the machine.