Necessity of starter in induction motor

Induction motor -Types of starter

1. Necessity of Starter Prepared by, Johny Renoald M.E., Ph.D

2. Introduction The three phase induction motors are self-starting due to rotating magnetic field. But the motors show tendency to draw very high current at the time of starting. Such a current can be 6 to 8 times of full load or rated current and it can damage the motor winding. Hence there should be a device which can limit such high starting current. Such a device which limits high starting current is called a starter.

3. Let us study in detail why starter is required for an induction motor. In a 3 phase induction motor, the magnitude of an induced EMF in the rotor circuit depends on the slip of the induction motor. Thus induced EMF effectively decides the magnitude of the rotor current . The rotor current in the running condition is given by :

4. Types: S tator rheostat starter Autotransformer starter Star-delta starter or switch Direct on line starter