1. An unexcited single phase synchronous motor is
a) reluctance motor
b) universal motor
c) repulsion motor
d) ac series motor
ans. a
2. The damping winding in a synchronous motor is generally used
a) to provide starting torque only
b) to reduce noise level
c) to reduce eddy currents
d) to prevent hunting and provide the starting torque
ans. d
3. A synchronous motor working on leading power factor and not driving any mechanical load is known as
a) synchronous induction motor
b) spinning motor
c) synchronous condenser
d) none of the above
ans. c
4. The amortisseur winding in a synchronous motor
a) provides starting torque only
b) provides starting torque and eliminates hunting
c) improves the power factor of the machine.
d) none of these
ans. b
5. An over excited synchronous motor operates at
a) unity power factor
b) lagging power factor
c) leading power factor
d) none of these
ans. c
6. Under full load running condition , the slip of a synchronous motor is
a) 0
b) about 0.2
c) about 0.01
d) none of these
ans. a
7. When the synchronous motor is to be started, the field system is energised
a) in the very beginning
b) after the motor has attained a speed slightly less than the synchronous speed
c) after the motor has attained synchronous speed and has been loaded
d) none of these
ans. b
8. When a synchronous motor is started, the field winding is initially
a) short circuited
b) open circuited
c) excited by a dc source
d) none of these
ans. a
9. V-curves of a synchronous motor show the relation between
a) armature current and field current
b) applied voltage and field current
c) applied voltage and armature current
d) none of these
ans. a
10. For a given load , the armature current of a synchronous motor is minimum when the power factor is
a) unity
b) slightly less than unity and lagging
c) slightly less than unity and leading
d) none of these
ans. a
a) reluctance motor
b) universal motor
c) repulsion motor
d) ac series motor
ans. a
2. The damping winding in a synchronous motor is generally used
a) to provide starting torque only
b) to reduce noise level
c) to reduce eddy currents
d) to prevent hunting and provide the starting torque
ans. d
3. A synchronous motor working on leading power factor and not driving any mechanical load is known as
a) synchronous induction motor
b) spinning motor
c) synchronous condenser
d) none of the above
ans. c
4. The amortisseur winding in a synchronous motor
a) provides starting torque only
b) provides starting torque and eliminates hunting
c) improves the power factor of the machine.
d) none of these
ans. b
5. An over excited synchronous motor operates at
a) unity power factor
b) lagging power factor
c) leading power factor
d) none of these
ans. c
6. Under full load running condition , the slip of a synchronous motor is
a) 0
b) about 0.2
c) about 0.01
d) none of these
ans. a
7. When the synchronous motor is to be started, the field system is energised
a) in the very beginning
b) after the motor has attained a speed slightly less than the synchronous speed
c) after the motor has attained synchronous speed and has been loaded
d) none of these
ans. b
8. When a synchronous motor is started, the field winding is initially
a) short circuited
b) open circuited
c) excited by a dc source
d) none of these
ans. a
9. V-curves of a synchronous motor show the relation between
a) armature current and field current
b) applied voltage and field current
c) applied voltage and armature current
d) none of these
ans. a
10. For a given load , the armature current of a synchronous motor is minimum when the power factor is
a) unity
b) slightly less than unity and lagging
c) slightly less than unity and leading
d) none of these
ans. a
