selection of electrical contactor

Selection of an electrical contactor

The DOL Starter

In the selection of dol starting of the motor, for the selection of the contactor, we select  1.5 times of full load current of the motor.

For example -

Suppose that if full load current of the motor is 100A. For the selection of a contactor of rating is = full load current * 1.5

means we used a 150A rating of the contactor or more than the 150A rating of the contactor.  

For the selection of a contactor in a star-delta starter

Rating of a star contactor 

Star contactor rating in a star-delta starter is one-third times of the motor full load current. or 33.3 per cent of motor full load current.

Suppose that if full load current of the motor is 100A. For the selection of a star contactor rating is = full load current * 1/3.

means we used a 33.3A rating of the contactor or more than the 33.3A rating of the contactor.

Rating of the delta contactor 

delta contactor rating in a star-delta starter is  57.73 per cent of the motor's full load current.

Suppose that if full load current of the motor is 100A. For the selection of a delta contactor rating is = full load current * 57.73 per cent.

means we used a 57.73A rating of the contactor or more than the 57.73A rating of the contactor. 

Know about this

1. What is a contactor and its working principles
2. Types of electrical contactors