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Electrical Engineering · Q48

Single Phase Induction Motors

Engineering and GATE · Electrical Engineering · question 48

Q48

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

A.
Magnetic relay
B.
Thermal relay
C.
Centrifugal switch
Answer
D.
None of the above

Answer: Option C

Solution

Answer: Option C
Solution:
In a single phase induction motor, the starting winding is used only during starting to provide the necessary starting torque.

Once the motor reaches about 70–80% of its rated speed, the starting winding must be disconnected to prevent overheating and energy loss.

This disconnection is achieved automatically by a centrifugal switch, which operates due to the centrifugal force developed as the rotor speed increases.

A magnetic relay and a thermal relay are mainly used for protection purposes, not for disconnecting the starting winding in this application.

Hence, the starting winding of a refrigerator motor is disconnected by a centrifugal switch, making Option C the correct answer.