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Polyphase Induction Motors - section-1
  1. Insertion of resistance in the stator of an induction motor

    2. A.

     Increases the load torque
    B.

     Decreases the starting torque
    C.

     Increases the starting torque
    D.

     None of the above

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  2. In a star-delta starter of an induction motor

    3. A.

     Resistance is inserted in the stator
    B.

     Reduced voltage is applied to the stator
    C.

     Resistance is inserted in the rotor
    D.

     Applied voltage per stator phase is 57.7% of the line voltage

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  3. The shape of the torque/slip curve of induction motor is

    4. A.

     Parabola
    B.

     Hyperbola
    C.

     Rectangular parabola
    D.

     Straight line

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

    5. A.

     Star connected only
    B.

     Delta connected only
    C.

     Both (A) and (B)
    D.

     None of the above

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  5. In squirrel cage induction motors, the rotor slots are usually given slight skew in order to

    6. A.

     Reduce windage losses
    B.

     Reduce eddy currents
    C.

     Reduce accumulation of dirt and dust
    D.

     Reduce magnetic hum

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  6. In a three-phase induction motor

    7. A.

     Power factor at starting is high as compared to that while running
    B.

     Power factor at starting is low as compared to that while running
    C.

     Power factor at starting in the same as that while running
    D.

     None of these

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

    8. A.

     Slip
    B.

     Rotor current
    C.

     Running torque
    D.

     Line voltage

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  8. In a squirrel cage motor the induced e.m.f. is

    9. A.

     Dependent on the shaft loading
    B.

     Dependent on the number of slots
    C.

     Slip times the stand still e.m.f. induced in the rotor
    D.

     None of the above

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  9. Size of a high speed motor as compared to low speed motor for the same H.P. will be

    10. A.

     Bigger
    B.

     Smaller
    C.

     Same
    D.

     Any of the above

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

    11. A.

     Less than 1 %
    B.

     1.5 %
    C.

     2 %
    D.

     4 %

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