Synchronous Motor Multiple Choice Questions - Set 04 - ObjectiveBooks

Synchronous Motor Multiple Choice Questions - Set 04

Practice Test: Question Set - 04

1. 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
    (A) Locked-rotor torque
    (B) Synchronous torque
    (C) Pull up torque
    (D) Reluctance torque

2. In a synchronous motor, the breakdown torque is
    (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

3. A three-phase synchronous motor will have
    (A) No slip-rings
    (B) One slip-ring
    (C) Two slip-rings
    (D) Three slip-rings

4. The synchronous motor is not inherently self-starting because
    (A) The force required to accelerate the rotor to the synchronous speed in an instant is absent
    (B) The starting device to accelerate the rotor to near synchronous speed is absent
    (C) A rotating magnetic field does not have enough poles
    (D) The rotating magnetic field is produced by only 50 Hz frequency currents

5. A synchronous motor can operate at
    (A) Lagging power factor only
    (B) Leading power factor only
    (C) Unity power factor only
    (D) Lagging, leading and unity power factors

6. The rotor copper losses, in a synchronous motor, are met by
    (A) D.C. source
    (B) Armature input
    (C) Motor input
    (D) Supply lines

7. A synchronous motor working at leading power factor can be used as
    (A) Voltage booster
    (B) Phase advancer
    (C) Noise generator
    (D) Mechanical synchronizer

8. When the rotor speed, in a synchronous machine, becomes more than the synchronous speed during hunting, the damper bars develop
    (A) Inductor motor torque
    (B) Induction generator torque
    (C) Synchronous motor torque
    (D) D.C. motor toque

9. While starting a salient pole synchronous motor by induction motor action and connecting field discharge resistance across field, starting and accelerating torque is produced by
    (A) Induction motor torque in field winding
    (B) Induction motor torque in damper winding
    (C) Eddy current and hysteresis torque in pole faces
    (D) All of the above methods

10. In which of the following motors the stator and rotor fields rotate simultaneously?
    (A) D.C. motor
    (B) Reluctance motor
    (C) Universal motor
    (D) Synchronous motor

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