1. Synchronous motors generally have
a) cylindrical rotor
b) salient pole rotor
c) both a and b are correct
d) none of these
ans. b
2. A synchronous motor is supplying a certain load and is operating at unity power factor. If field current and terminal voltage are kept constant but the load is increased, the power factor
a) will remain the same
b) will become leading
c) will become lagging
d) none of these
ans. c
3. Synchronous motors are usually operated at
a) unity power factor
b) leading power factor
c) lagging power factor
d) none of these
ans. b
4. A salient pole synchronous motor is running at no load. Its field current is switched off. The motor will
a) come to stop
b) continue to run at synchronous speed
c) continue to run at speed slightly less than synchronous speed
d) none of these
ans. c
5. In a synchronous motor
a) the generated emf must always be less than the terminal voltage
b) the generated emf must always be more than the terminal voltage
c) the generated emf can be less than or greater than the terminal voltage
d) none of these
ans. c
6. As the load on a synchronous motor is increased, the torque angle
a) increases
b) decreases
c) remains the same
d) none of these
ans. a
7. An under excited synchronous motor operates at
a) unity power factor
b) leading power factor
c) lagging power factor
d) none of these
ans. c
8. Synchronous motors are used in
a) sizes greater than about 50 HP
b) all sizes
c) generally small sizes
d) none of these
ans. a
9. A synchronous motor is supplying its rated load. If the excitation is increased
a) the power factor becomes more leading
b) the power factor becomes more lagging
c) the power factor becomes less lagging
d) none of these
ans. a
10. The power output of a synchronous motor is
a) directly proportional to synchronous reactance
b) inversely proportional to synchronous reactance
c) independent of synchronous reactance
d) none of these
ans. b
a) cylindrical rotor
b) salient pole rotor
c) both a and b are correct
d) none of these
ans. b
2. A synchronous motor is supplying a certain load and is operating at unity power factor. If field current and terminal voltage are kept constant but the load is increased, the power factor
a) will remain the same
b) will become leading
c) will become lagging
d) none of these
ans. c
3. Synchronous motors are usually operated at
a) unity power factor
b) leading power factor
c) lagging power factor
d) none of these
ans. b
4. A salient pole synchronous motor is running at no load. Its field current is switched off. The motor will
a) come to stop
b) continue to run at synchronous speed
c) continue to run at speed slightly less than synchronous speed
d) none of these
ans. c
5. In a synchronous motor
a) the generated emf must always be less than the terminal voltage
b) the generated emf must always be more than the terminal voltage
c) the generated emf can be less than or greater than the terminal voltage
d) none of these
ans. c
6. As the load on a synchronous motor is increased, the torque angle
a) increases
b) decreases
c) remains the same
d) none of these
ans. a
7. An under excited synchronous motor operates at
a) unity power factor
b) leading power factor
c) lagging power factor
d) none of these
ans. c
8. Synchronous motors are used in
a) sizes greater than about 50 HP
b) all sizes
c) generally small sizes
d) none of these
ans. a
9. A synchronous motor is supplying its rated load. If the excitation is increased
a) the power factor becomes more leading
b) the power factor becomes more lagging
c) the power factor becomes less lagging
d) none of these
ans. a
10. The power output of a synchronous motor is
a) directly proportional to synchronous reactance
b) inversely proportional to synchronous reactance
c) independent of synchronous reactance
d) none of these
ans. b
