Single Phase Induction Motors MCQ Questions & Answers

41

Which of the following motor will have relatively higher power factor ?

A) Capacitor run motor B) Shaded pole motor C) Capacitor start motor D) Split phase motor

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Answer & Solution

Answer: Option A

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42

In split-phase motor auxiliary winding is of

A) thick wire placed at the bottom of the slots B) thick wire placed at the top of the slots C) thin wire placed at the top of the slots D) thin wire placed at the bottom of the slots

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Answer & Solution

Answer: Option C

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43

In a capacitor start and run motors the function of the running capacitor in series with the auxiliary winding is to

A) improve power factor B) increase overload capacity C) reduce fluctuations in torque D) to improve torque

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Answer & Solution

Answer: Option A

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44

Which of the following single-phase induction motors is generally used in time phonographs?

A) Resistance start B) Capacitor start capacitor run C) Shaded pole D) Universal

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Answer & Solution

Answer: Option C

Solution:

Shaded pole motors are commonly used in applications like time phonographs due to their simple construction and reliable operation.

They have low starting torque, which is suitable for devices that require consistent and low-speed operation.

These motors are also inexpensive and have a long lifespan, making them ideal for such applications.

45

In a capacitor start motor, the phase displacement between starting and running winding can be nearly

A) 10° B) 30° C) 60° D) 90°

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Answer & Solution

Answer: Option D

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46

After the starting winding of a single phase induction motor is disconnected from supply, it continues to run only on

A) running winding B) rotor winding C) field winding D) compensating winding

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Answer & Solution

Answer: Option A

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47

The power factor of a single-phase induction motor is usually

A) lagging B) always leading C) unity D) unity to 0.8 leading

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Answer & Solution

Answer: Option A

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48

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 D) None of the above

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Answer & 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.

49

To reverse the direction of rotation of acapacitor start motor while it is running we should

A) disconnect motor from the supply till it stops then reconnect it to supply with reversed connection of main or auxiliary winding B) disconnect motor from supply and immediately reconnect it to supply with reversed con-nections of the main winding C) reverse the direction of connection of the auxiliary winding and after motor comes to rest then connect auxiliary winding to the supply D) reverse the direction of connections of the auxiliary winding and immediately connect it to supply

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Answer & Solution

Answer: Option A

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50

A universal motor is one which

A) can be operated either on D.C. or A.C. supply at approximately the same speed and output B) can be marketed internationally C) runs at dangerously high speed on no-load D) none of the above

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Answer & Solution

Answer: Option A

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Single Phase Induction Motors MCQ Questions & Answers | Electrical Engineering