Induction motor MCQ

01. No load test of 3-phase induction motor used to determine

Variable loss

Constant loss

Eddy current loss only

Hysteresis loss only


02. Blocked rotor test in an induction motor is used to determine

Leakage impedance

Copper loss

Both a & b

None of the above


03. Which of the following losses are negligible in blocked rotor test?

Mechanical losses

Iron losses

Both a & b

None of the above


04. In induction generator operation the slip is always

Positive

Negative

Infinite

Zero


05. In an induction motor if the air gap is increased than which of the following statement is correct

Power factor will decrease

Power factor will increase

Speed will increase

Speed will decrease


06. If the applied rated voltage per phase is reduced to one-half, then the starting torque of squirrel cage induction motor becomes

4 times the initial value

2 times the initial value

1/4 of the initial value

1/2 times the initial value


07. The value of power factor of an induction motor operating at no load is

0.9 lagging

Unity

0.2 lead

0.2 lag


08. what is the ratio of rotor input power to rotor copper loss in an induction motor?

1/(1 – S)

1 – S

1/S

S

09. Semi closed slots or totally closed slots are used in induction motors to improve

Starting current

Starting Torque

Power Factor

Pull-out Torque


10. The rotor slots are slightly skewed in squirrel cage induction motor in order to

Increasing Rotor bar strength

Prevent cogging effect

Both 1 & 2

None of the above


11. If an induction machine is run at above the synchronous speed it acts as

Synchronous Motor

Synchronous Generator

Induction Generator

None of the above


12. The best method to increase the starting torque of a 3-phase slip ring induction motor is

Rotor Resistance

Supply voltage

Supply Frequency

None of the above


13. A small air gap in 3 phase induction motor helps to

Reduce cogging effect

Reduce Crawling effect

Reduce Magnetizing effect

All of the above


14. Induction motors have the advantage of

Less Maintenace

Less cost

Simple in construction

All of the above


15. The rotor power output of a 3-phase induction motor is 30 KW and corresponding slip is 4%. The rotor copper loss will be

625 Watt

250 Watt

1000 Watt

1250 Watt

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