Chapter 9, Problem 1RQ

What is the purpose of a starting relay?

1. a. to start an electric motor
2. b. to remove the starting winding or component from the circuit
3. c. to protect the motor from starting overloads
4. d. to prevent the motor from starting under heavy loads

To determine

The correct option for the purpose of the starting relay.

Explanation of Solution

The given choices are,

1. a) to start an electric motor
2. b) to remove the starting winding or component from the circuit
3. c) to protect the motor from starting overloads
4. d) to prevent the motor from starting under heavy loads

The starting relay is the relay that operates on the principle of back emf. The starting relay is used with a starting winding of single phase motor. This relay control the starting winding, as the single phase motor operates a back emf is produced in the starting winding, this winding acts as the generator that produce back emf which further corresponds to the motor speed. Thus the starting relay is used to drop the starting winding as a predefined back emf is produced in the winding.

Thus, the use of starting relay is to remove the starting winding or component from the circuit.

Thus, the correct option is (b)