MCQ Or Quiz On Three Phase Induction Motor

Hello Guys, welcome back to my blog. In this article, I will discuss the quiz on three phase induction motor, objective type questions related to the three-phase induction motor.

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Quiz On Three Phase Induction Motor

01. The silicon steel is fabricated by which of the following components?

  • (a) Bearings
  • (b) Shaft
  • (c) Stator core
  • (d) None of the above

Ans: c

02. In the induction motor, the frame is usually made of

  • (a) silicon steel
  • (b) cast iron
  • (c) aluminum
  • (d) bronze

Ans: b

03. In the induction motor, the shaft is made of

  • (a) stiff
  • (b) flexible
  • (c) hollow
  • (d) any of the above

Ans: a

04. The material used to make the shaft of an induction motor?

  • (a) high-speed steel
  • (b) stainless steel
  • (c) carbon steel
  • (d) cast iron

Ans: c

05. At no-load, the slip in an induction motor is generally?

  • (a) less than 1%
  • (b) 1.5%
  • (c) 2%
  • (d) 4%

Ans: a

06. The slip in a medium-sized induction motor is generally around?

  • (a) 0.04%
  • (b) 0.4%
  • (c) 4%
  • (d) 14%

Ans: c

07. The rotor slots in a squirrel-cage induction motor are usually given a slight skew in order to?

  • (a) reduce windage losses
  • (b) reduce eddy currents
  • (c) reduce the accumulation of dust and dirt
  • (d) reduce magnetic hum

Ans: d

08. If the air gap in an induction motor is increased?

  • (a) the rotor magnetizing current will decrease
  • (b) the power factor will decrease
  • (c) speed of the motor will increase
  • (d) the windage losses will increase

Ans: b

09. The material used to make Slip rings?

  • (a) copper
  • (b) carbon
  • (c) phosphor bronze
  • (d) aluminum

Ans: c

10. Find the frequency of the rotor e.m.f, if the frequency of the three-phase induction motor is 50 Hz and slip is of 4%?

  • (a) 200 Hz
  • (b) 50 Hz
  • (c) 2 Hz
  • (d) 0.2 Hz

Ans: c

11. The s is the slip and Ns is the synchronous speed, then the actual running speed of the motor will be

  • (a) Ns
  • (b) s.N,
  • (c) (l-s)Ns
  • (d) (Ns-l)s

Ans: c

12. The efficiency of the induction motor is?

  • (a) 60 to 90%
  • (b) 80 to 90%
  • (c) 95 to 98%
  • (d) 99%

Ans: b

13. In the squirrel-cage induction motor, the number of slip rings is usually?

  • (a) two
  • (b) three
  • (c) four
  • (d) none

Ans: d

14. In a squirrel-cage induction motor, the starting torque is usually?

  • (a) low
  • (b) negligible
  • (c) same as full-load torque
  • (d) slightly more than full-load torque

Ans: a

15. The double squirrel-cage induction motor has two?

  • (a) rotors moving in the opposite direction
  • (b) parallel windings in the stator
  • (c) parallel windings in the rotor
  • (d) series windings in the stator

Ans: c

16. The Star-delta starting of motors is not usually applicable in case of?

  • (a) single-phase motors
  • (b) variable speed motors
  • (c) low horsepower motors
  • (d) high-speed motors

Ans: a

17. The term ‘cogging’ is associated with

  • (a) three-phase transformers
  • (b) compound generators
  • (c) D.C. series motors
  • (d) induction motors

Ans: d

18. The torque in the induction motor is?

  • (a) inversely proportional to (Islip)
  • (b) directly proportional to (slip)2
  • (c) inversely proportional to slip
  • (d) directly proportional to slip

Ans: d

19. An induction motor with a speed of 1000 r.p.m. will have how many numbers of poles?

  • (a) 8 poles
  • (b) 6 poles
  • (c) 4 poles
  • (d) 2 poles

Ans: b

20. In the induction motor, the good power factor can be achieved if the average flux density in the air gap is?

  • (a) absent
  • (b) small
  • (c) large
  • (d) infinity

Ans: b

21. An induction motor is also called as?

  • (a) D.C. compound motor
  • (b) D.C. series motor
  • (c) synchronous motor
  • (d) asynchronous motor

Ans: d

22. In an induction motor, the injected emf must-have?

  • (a) zero frequency
  • (b) the same frequency as the slip frequency
  • (c) the same phase as the rotor e.m.f.
  • (d) high value for the satisfactory speed control

Ans: b

23. To control the speed of the squirrel-cage induction motor which of the following method can easily applicable?

  • (a) By changing the number of stator poles
  • (b) Rotor rheostat control
  • (c) By operating two motors in cascade
  • (d) By injecting e.m.f. in the rotor circuit

Ans: a

24. In the induction motor, the crawling is caused by

  • (a) low voltage supply
  • (b) high loads
  • (c) harmonics developed in the motor
  • (d) improper design of the machine
  • (e) none of the above

Ans: c

25. To start the cage induction motor, the auto-starter can be used for which of the following type?

  • (a) star connected only
  • (b) delta connected only
  • (c) (a) and (b) both
  • (d) none of the above

Ans: c

I hope this article “quiz on three phase induction motor” may help you all a lot. Thank you for reading. If you have any doubts related to quiz on three phase induction motor, then comment below.

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Chetan Shidling

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