1. The magnitude of the emf induced in the stator due to revolving flux will depend upon the
a) speed of the motor
b) dc excitation current
c) load on the motor
d) speed and rotor flux
ans. b
2. If the field of synchronous motor is under excited, the power factor will be
a) more than unity
b) unity
c) lagging
d) leading
ans. c
3. If one of the 3-phase of synchronous motor is short circuited, motor will
a) start
b) not start
c) over heated
d) fail to pull into synchronism
ans. b
4. The advantages of synchronous motor over slipring induction motor are that it's
a) power factor can be varied
b) speed can be easily varied
c) speed is independent of supply frequency
d) rotor has two slip rings
ans. a
5. The standard full load power factor of a synchronous motor is
a) unity
b) unity or 0.8 leading
c) unity or 0.8 lagging
d) zero or 0.8 leading
ans. b
6. The synchronous motor can be started by
a) coupling with dc compound motor
b) coupling with ac induction motor
c) providing damper windings
d) all of these
ans. d
7. The advantages of synchronous motor as compared to induction motor are that
a) it runs at constant speed
b) it can run over wide range of power factors both lagging and leading
c) it's torque is less sensitive to change in supply voltage
d) all of these
ans. d
8. Rotor winding of the synchronous motor is excited by
a) induction from stator current
b) ac supply
c) dc supply supplied by the exciter
d) the revolving field
ans. c
9. The speed of synchronous motor depends upon
a) number of poles
b) supply frequency
c) either a or b
d) both a and b are correct
ans. d
10. The magnitude of the induced emf in the stator of a synchronous motor
a) is equal to the supply voltage
b) is less than the supply voltage
c) can be increased than the supply voltage
d) can be increased or decreased than the supply voltage
ans. d
a) speed of the motor
b) dc excitation current
c) load on the motor
d) speed and rotor flux
ans. b
2. If the field of synchronous motor is under excited, the power factor will be
a) more than unity
b) unity
c) lagging
d) leading
ans. c
3. If one of the 3-phase of synchronous motor is short circuited, motor will
a) start
b) not start
c) over heated
d) fail to pull into synchronism
ans. b
4. The advantages of synchronous motor over slipring induction motor are that it's
a) power factor can be varied
b) speed can be easily varied
c) speed is independent of supply frequency
d) rotor has two slip rings
ans. a
5. The standard full load power factor of a synchronous motor is
a) unity
b) unity or 0.8 leading
c) unity or 0.8 lagging
d) zero or 0.8 leading
ans. b
6. The synchronous motor can be started by
a) coupling with dc compound motor
b) coupling with ac induction motor
c) providing damper windings
d) all of these
ans. d
7. The advantages of synchronous motor as compared to induction motor are that
a) it runs at constant speed
b) it can run over wide range of power factors both lagging and leading
c) it's torque is less sensitive to change in supply voltage
d) all of these
ans. d
8. Rotor winding of the synchronous motor is excited by
a) induction from stator current
b) ac supply
c) dc supply supplied by the exciter
d) the revolving field
ans. c
9. The speed of synchronous motor depends upon
a) number of poles
b) supply frequency
c) either a or b
d) both a and b are correct
ans. d
10. The magnitude of the induced emf in the stator of a synchronous motor
a) is equal to the supply voltage
b) is less than the supply voltage
c) can be increased than the supply voltage
d) can be increased or decreased than the supply voltage
ans. d
