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EEE :: Synchronous Motors

  1. The maximum power developed in a synchronous motor occurs at a coupling angle of

  2. A.

     30°

    B.

     60°

    C.

     90°

    D.

     180°

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  3. When the stator windings are connected in such a fashion that the number of poles are made half, the speed of the rotor of a synchronous motor

  4. A.

     remains same as the original value

    B.

     decreases to half the original value

    C.

     tends to becomes zero

    D.

     increases to two times the original value

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  5. The speed of a synchronous motor

  6. A.

     increases as the load increases

    B.

     decreases as the load decreases

    C.

     always remains constant

    D.

     none of the above

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  7. In which of the following motors the stator and rotor magnetic field rotate at the same speed ?

  8. A.

     Universal motor

    B.

     Synchronous motor

    C.

     Induction motor

    D.

     Reluctance motor

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  9. In a synchronous motor, the breakdown torque is

  10. A.

     directly proportional to applied voltage

    B.

     directly proportional to the square of the applied voltage

    C.

     inversely proportional to applied voltage

    D.

     none of the above

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  11. The angle between the rotating stator flux and rotor poles is called _____ angle.

  12. A.

     torque

    B.

     obtuse

    C.

     synchronizing

    D.

     power factor

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  13. A 3-phase synchronous motor is running clockwise. If the direction of its field current is reversed

  14. A.

     the motor will stop

    B.

     the motor continue to run in the same direction

    C.

     the winding of the motor will burn

    D.

     the motor will run in the reverse direction

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  15. Due to which of the following reasons a synchronous motor fails to pull into synchronism after applying D.C. field current?

  16. A.

     High field current

    B.

     Low short circuit ratio

    C.

     High core losses

    D.

     Low field current

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  17. When the rotor speed, in a synchronous machine, becomes more than the synchronous speed during hunting, the damper bars develop

  18. A.

     inductor motor torque

    B.

     induction generator torque

    C.

     synchronous motor torque

    D.

     d.c. motor toque

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  19. The working of a synchronous motor is similar to

  20. A.

     gear train arrangement

    B.

     transmission of mechancial power by shaft

    C.

     distribution transformer

    D.

     turbine

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