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EEE :: Synchronous Motors

  1. The power developed by a synchronous motor will be maximum when the load angle is

  2. A.

     zero

    B.

     45°

    C.

     90°

    D.

     120°


  3. In a synchronous motor, V-curves represent relation between

  4. A.

     armature current and field current

    B.

     power factor and speed

    C.

     field current and speed

    D.

     field current and power factor


  5. The maximum torque which a synchronous motor will develop at rest for any angular position of the rotor, at rated stator supply voltage and frequency, is known as

  6. A.

     locked-rotor torque

    B.

     synchronous torque

    C.

     pull up torque

    D.

     reluctance torque


  7. In a synchronous motor, the armature current has large values for

  8. A.

     high excitation only

    B.

     low excitation only

    C.

     both high and low excitation

    D.

     none of the above


  9. The coupling angle or load angle of synchronous motor is defined as the angle between the

  10. A.

     rotor and stator teeth

    B.

     rotor and the stator poles of opposite polarity

    C.

     rotor and the stator poles of the same polarity

    D.

     none of the above


  11. The armature current of the synchronous motor

  12. A.

     has large values for low excitation i niy

    B.

     has large values for high excitation only

    C.

     has large values for low and high excitation

    D.

     any of the above


  13. If in a synchronous motor, driving mechanical load and drawing current at lagging power factor from constant voltage supply, its field excitation is increased, then its power factor

  14. A.

     become more

    B.

     become less

    C.

     remain constant

    D.

     none of the above


  15. The maximum value of torque that a synchronous motor can develop without losing its synchronism, is known as

  16. A.

     slip torque

    B.

     pull-out torque

    C.

     breaking torque

    D.

     synchronising torque


  17. Exciters of synchronous machines are

  18. A.

     d.c. shunt machines

    B.

     d.c. series machines

    C.

     d.c. compound machines

    D.

     any of the above


  19. A synchronous motor running with normal excitation adjusts to load increases essentially by increase in

  20. A.

     back e.m.f.

    B.

     armature current

    C.

     power factor

    D.

     torque angle