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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