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Polyphase Induction Motors - section-1
  1. An induction motor can run at synchronous speed when

    2. A.

     It is run on load
    B.

     It is run in reverse direction
    C.

     It is run on voltage higher than the rated voltage
    D.

     e.m.f. is injected in the rotor circuit

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  2. Slip ring motor is preferred over squirrel cage induction motor where

    3. A.

     High starting torque is required
    B.

     Load torque is heavy
    C.

     Heavy pull out torque is required
    D.

     All of the above

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  3. A change of 4% of supply voltage to an induction motor will produce a change of approximately

    4. A.

     4% in the rotor torque
    B.

     8% in the rotor torque
    C.

     12% in the rotor torque
    D.

     16% in the rotor torque

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  4. If an induction motor with certain ratio of rotor to stator slots, runs at 1/7 of the normal speed, the phenomenon will be termed as

    5. A.

     Humming
    B.

     Hunting
    C.

     Crawling
    D.

     Cogging

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  5. The 'cogging' of an induction motor can be avoided by

    6. A.

     Proper ventilation
    B.

     Using DOL starter
    C.

     Autotransformer starter
    D.

     Having number of rotor slots more or less than the number of stator slots (not equal)

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  6. The power scale of circle diagram of an induction motor can be found from

    7. A.

     Stator resistance test
    B.

     No-load test only
    C.

     Short-circuit test only
    D.

     None of the above

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  7. In a three-phase induction motor, the number of poles in the rotor winding is always

    8. A.

     Zero
    B.

     More than the number of poles in stator
    C.

     Less than number of poles in stator
    D.

     Equal to number of poles in stator

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  8. Which type of bearing is provided in small induction motors to support the rotor shaft?

    9. A.

     Ball bearings
    B.

     Cast iron bearings
    C.

     Bush bearings
    D.

     None of the above

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  9. The vafcie of transformation ratio of an induction motor can be found by

    10. A.

     Open-circuit test only
    B.

     Short-circuit test only
    C.

     Stator resistance test
    D.

     None of the above

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  10. An induction motor is identical to

    11. A.

     D.C. compound motor
    B.

     D.C. series motor
    C.

     Synchronous motor
    D.

     Asynchronous motor

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