3-PHASE INDUCTION MOTOR - 2

11. The starting torque of a squirrel cage induction motor is ________

low

negligible

same as full load torque

slightly more than full load torque

12. A double squirrel cage induction motor has__________

two rotors moving in opposite directions

two parallel windings in stator

two parallel windings in rotor

two series windings in stator

13. Star-delta starting of motors is not possible in case of _________

single phase motors

variable speed motots

low horse power motors

high speed motors

14. In case of the induction motors the torque is ___________

inversely proportional to (√slip )

directly proportional to (slip)2

inversely proportional to slip

directly propotional to slip

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

8 poles

6 poles

4 poles

2 poles

16. The good power factor of an induction motor can be achieved if the average flux density in the air gap is ___________

absent

small

large

infinity

17. Which of the following methods is easily applicable to control the speed of the squirrel-cage induction motor?

by changing the number of stator poles

rotor rheostat control

by operating two motors in cascade

by injecting e.m.f. in the rotor circuit

18. The auto-starters (using three auto transformers) can be used to start cage induction motor of the following type _____________

star connected only

delta connected only

both a & b

none of the above

19. It is advisable to avoid line-starting of induction motor and use starter because ______

motor takes five to seven times its full load current

it will pick-up very high speed and may go out of step

it will run in reverse direction

starting torque is very high

20. Rotor rheostat control method of speed control is used for __________

squirrel-cage induction motors only

slip ring induction motors only

both a & b

none of the above

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