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Single Phase Induction Motors

Study 110 Electrical Engineering MCQs with correct answers and explanations.

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61Electrical EngineeringMedium

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

AResistance start

BCapacitor start capacitor run

CUniversal

DShaded pole

Correct answer

D. Shaded pole

Explanation

The correct answer is Shaded pole.

62Electrical EngineeringMedium

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

Adisconnect motor from the supply till it stops then reconnect it to supply with reversed connection of main or auxiliary winding

Breverse the direction of connections of the auxiliary winding and immediately connect it to supply

Creverse the direction of connection of the auxiliary winding and after motor comes to rest then connect auxiliary winding to the supply

Ddisconnect motor from supply and immediately reconnect it to supply with reversed connections of the main winding

Correct answer

A. disconnect motor from the supply till it stops then reconnect it to supply with reversed connection of main or auxiliary winding

Explanation

The correct answer is disconnect motor from the supply till it stops then reconnect it to supply with reversed connection of main or auxiliary winding.

63Electrical EngineeringMedium

A centrifugal switch is used to dis- connect ‘starting winding when motor has________?

Arun for about 5 minutes

Brun for about 1 minute

Cpicked up about 50 to 70 per cent of rated speed

Dpicked up about 10 to 25 per cent of rated speed

Correct answer

C. picked up about 50 to 70 per cent of rated speed

Explanation

The correct answer is picked up about 50 to 70 per cent of rated speed.

64Electrical EngineeringMedium

In repulsion motor, maximum torque is developed when________?

Abrush axis is at 45° electrical to the field axis

Bbrush axis is at 90° electrical to the field axis

Cbrush axis coincides with the field axis

Dnone of the above

Correct answer

A. brush axis is at 45° electrical to the field axis

Explanation

The correct answer is brush axis is at 45° electrical to the field axis.

65Electrical EngineeringMedium

The speed of a universal motor is generally reduced by using________?

AV-belts

Bgear trains

Cbrakes

Dchains

Correct answer

B. gear trains

Explanation

The correct answer is gear trains.

66Electrical EngineeringMedium

In case of a reluctance motor, when the load is increased so that it cannot maintain synchronous speed the motor will________?

Arun as induction motor

Bdraw excessive armature current and may burn out

Cbecome unstable

Dfall out of synchronism and come to stand still

Correct answer

A. run as induction motor

Explanation

The correct answer is run as induction motor.

67Electrical EngineeringMedium

A single-phase induction motor is________?

Ainherently self-starting with low torque

Binherently non-self-starting with low torque

Cinherently non-self-starting with high torque

Dinherently self-starting with high torque

Correct answer

B. inherently non-self-starting with low torque

Explanation

The correct answer is inherently non-self-starting with low torque.

68Electrical EngineeringMedium

Which of the following motors is used in tape-recorders ________?

AReluctance motor

BCapacitor-run motor

CHysteresis motor

DUniversal motor

Correct answer

C. Hysteresis motor

Explanation

The correct answer is Hysteresis motor.

69Electrical EngineeringMedium

In a capacitor start single-phase motor, when capacitor is replaced by a resistance________?

Athe motor will consume less power

Bmotor will run in reverse direction

Cmotor will continue to run in same direction

Dtorque will increase

Correct answer

C. motor will continue to run in same direction

Explanation

The correct answer is motor will continue to run in same direction.

70Electrical EngineeringMedium

Direction of rotation of a split phase motor can be reversed by reversing the connection of________?

Aboth A. and (b)

Brunning winding only

Ceither A. or (b)

Dstarting winding only

Correct answer

C. either A. or (b)

Explanation

The correct answer is either A. or (b).

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

Adisconnect motor from the supply till it stops then reconnect it to supply with reversed connection of main or auxiliary winding

Breverse the direction of connections of the auxiliary winding and immediately connect it to supply

Creverse the direction of connection of the auxiliary winding and after motor comes to rest then connect auxiliary winding to the supply

Ddisconnect motor from supply and immediately reconnect it to supply with reversed connections of the main winding

Correct answer

A. disconnect motor from the supply till it stops then reconnect it to supply with reversed connection of main or auxiliary winding

Explanation

The correct answer is disconnect motor from the supply till it stops then reconnect it to supply with reversed connection of main or auxiliary winding.

In repulsion motor, maximum torque is developed when________?

Abrush axis is at 45° electrical to the field axis

Bbrush axis is at 90° electrical to the field axis

Cbrush axis coincides with the field axis

Dnone of the above

Correct answer

A. brush axis is at 45° electrical to the field axis

Explanation

The correct answer is brush axis is at 45° electrical to the field axis.

A single-phase induction motor is________?

Ainherently self-starting with low torque

Binherently non-self-starting with low torque

Cinherently non-self-starting with high torque

Dinherently self-starting with high torque

Correct answer

B. inherently non-self-starting with low torque

Explanation

The correct answer is inherently non-self-starting with low torque.