Question

Explain the necessity of a starter in case of DC motor?

Answer 1

Necessity of Starter for DC Motors.
When the motor is at rest, the induced back e.m.f Eb in the armature is zero because the back e.m.f is directly proportional to the speed of the motor, (Ebα N). At starting time, therefore, the armature current is limited only by the resistance of the armature circuit.

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Answer 2

In dc motors the armature is generally designed to have the least resistance possible. So when starting a dc motor starter is connectedsuch that it limits the current value by being in series with armature and later seperates from the circuit. But by then back emf develops in the armature.