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EEE :: Polyphase Induction Motors

  1. The complete circle diagram of induction motor can be drawn with the help of data found from

  2. A.

     No-load test

    B.

     Blocked rotor test

    C.

     Stator resistance test

    D.

     All of the above


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

  4. A.

     8 poles

    B.

     6 poles

    C.

     4 poles

    D.

     2 poles


  5. Less maintenance troubles are experienced in case of

  6. A.

     Slip ring induction motor

    B.

     Squirrel cage induction motor

    C.

     Both (A) and (B)

    D.

     None of the above


  7. As load on an induction motor goes on increasing

  8. A.

     Its power factor goes on decreasing

    B.

     Its power factor remains constant

    C.

     Its power factor goes on increasing even after full load

    D.

     Its power factor goes on increasing up to full load and then it falls again


  9. The frame of an induction motor is usually made of

  10. A.

     Silicon steel

    B.

     Cast iron

    C.

     Aluminium

    D.

     Bronze


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

  12. A.

     200 Hz

    B.

     50 Hz

    C.

     2 Hz

    D.

     0.2 Hz


  13. DOL starting of induction motors is usually restricted to

  14. A.

     Low horsepower motors

    B.

     Variable speed motors

    C.

     High horsepower motors

    D.

     High speed motors


  15. In induction motor, percentage slip depends on

  16. A.

     Supply frequency

    B.

     Supply voltage

    C.

     Copper losses in motor

    D.

     None of the above


  17. Reduced voltage starter can be used with

  18. A.

     Slip ring motor only but not with squirrel cage induction motor

    B.

     Squirrel cage induction motor only but not with slip ring motor

    C.

     Squirrel cage as well as slip ring induction motor

    D.

     None of the above


  19. The speed of a squirrel-cage induction motor can be controlled by all of the following except

  20. A.

     Changing supply frequency

    B.

     Changing number of poles

    C.

     Changing winding resistance

    D.

     Reducing supply voltage