Induction motor mcqs

1. Which of the following component is usually fabricated out of silicon steel ?

(a) Bearings

(b) Shaft

(c) Stator core

(d) None of the above

2. In an induction motor, no-load the slip is generally

(a) less than 1%

(b) 1.5%

(c) 2%

(d) 4%

3. Slip rings are usually made of

1 point

(a) copper

(b) carbon

(c) phospor bronze

(d) aluminium

4. A 3-phase 440 V, 50 Hz induction motor has 4% slip. The frequency of rotor e.m.f. will be

1 point

(a) 200 Hz

(b) 50 Hz

(c) 2 Hz

(d) 0.2 Hz

5. The efficiency of an induction motor can be expected to be nearly

1 point

(a) 60 to 90%

(b) 80 to 90%

(c) 95 to 98%

(d) 99%

6. The number of slip rings on a squirrel cage induction motor is usually

1 point

(a) two

(b) three

(c) four

(d) none

7. The term 'cogging' is associated with

1 point

(a) three phase transformers

(b) compound generators

(c) D.C. series motors

(d) induction motors

8. An induction motor with 1000 r.p.m. speed will have

1 point

(a) 8 poles

(b) 6 poles

(c) 4 poles

(d) 2 poles

9. An induction motor is identical to

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(a) D.C. compound motor

(b) D.C. series motor

(c) synchronous motor

(d) asynchronous motor

10. The crawling in the induction motor is caused by

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(a) low voltage supply

(b) high loads

(c) harmonics develped in the motor

(d) improper design of the machine

11. In the circle diagram for induction motor, the diameter of the circle represents

1 point

(a) slip

(b) rotor current

(c) running torque

(d) line voltage

12. If any two phases for an induction motor are interchanged

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(a) the motor will run in reverse direction

(b) the motor will run at reduced speed

(c) the motor will not run

(d) the motor will burn

13. An induction motor is

1 point

(a) self-starting with zero torque

(b) self-starting with high torque

(c) self-starting with low torque

(d) non-self starting

14. The starting torque of a 3-phase squirrel cage induction motor is

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(a) twice the full load torque

(b) 1.5 times the full load torque

(c) equal to full load torque

15. In an induction motor if air-gap is increased

1 point

(a) the power factor will be low

(b) windage losses will be more

(c) bearing friction will reduce

(d) copper loss will reduce In an induction motor

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