Starting winding of a single-phase motor of a refrigerator is disconnected from the circuit by means of a

• A. None of these
• B. Thermal Relay
• C. Centrifugal Switch
• D. Magnetic Relay

Answer: (D)

The function of the starting relay provided in the refrigerator is to start the split-phase induction motor by connecting the auxiliary winding or starting winding across the main supply in addition to the main winding at the time of starting. This helps to make the split-phase inflection motor as the self-induction motor is unable to start.
The first method of disconnecting the starting winding of a split-phase motor is already discussed in the above Question i.e Question Number 63.
Another method of disconnecting the auxiliary winding when the motor has picked up speed is by using an electromagnetic relay as has been shown in Fig
The torque required to start the motor is significantly more than needed in the running condition At the starting time of the motor, electrical power is given to start relay and winding of the motor. It also provides current to the starting winding of the motor. The starting winding provides sufficient torque so that the motor starts running. As the motor speed increases, the torque requirement decreases and thereby the current required by the motor also decreases. The current in starting relay is not able to hold the relay and it gets released which opens the starting winding contacts. Therefore, the starting winding gets disconnected.