MCQ Or Quiz On Three Phase Induction Motor

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Also read – Electrical Machines Questions And Answers.

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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