1. A synchronous motor can run at
a) a leading power factor
b) unity power factor
c) lagging or leading or unity power factor
d) zero power factor
ans. c
2. The power factor of the input power to a synchronous motor is adjusted by varying
a) number of poles
b) magnitude of excitation
c) magnitude of armature reaction
d) none of these
ans. b
3. At constant load , the magnitude of armature current of a synchronous motor has large values for
a) low values of field excitation only
b) high values of field excitation only
c) both a and b
d) none of these
ans. c
4. For a synchronous motor, the inverter "V" curve is the relation between
a) field current and power factor
b) field current and armature current
c) armature current and power factor
d) none of these
ans. a
5. In a synchronous motor , minimum armature current occurs at
a) zero power factor
b) unity power factor
c) lagging power factor
d) leading power factor
ans. b
6. A 3-ring synchronous converter supplying a dc 3-wire system must have the secondary of its transformer connected as
a) delta only
b) delta or star
c) zig-zag only
d) star or zig-zag
ans. c
7. The construction of synchronous motor is similar to
a) dc compound motor
b) slip ring induction motor
c) dc shunt motor
d) alternator
ans. d
8. The synchronous motor runs at
a) less than synchronous speed
b) synchronous speed
c) more than synchronous speed
d) none of these
ans. b
9. The synchronous motor runs on
a) 3-phase ac supply
b) 3-phase dc and ac supply
c) dc supply only
d) 3-phase ac and single phase ac
ans. b
10. If a synchronous motor is switched on to 3-phase supply with its rotor winding short circuited, it will
a) start
b) not start
c) start and continue to run as induction motor
d) start and continue to run as synchronous motor
ans. c
a) a leading power factor
b) unity power factor
c) lagging or leading or unity power factor
d) zero power factor
ans. c
2. The power factor of the input power to a synchronous motor is adjusted by varying
a) number of poles
b) magnitude of excitation
c) magnitude of armature reaction
d) none of these
ans. b
3. At constant load , the magnitude of armature current of a synchronous motor has large values for
a) low values of field excitation only
b) high values of field excitation only
c) both a and b
d) none of these
ans. c
4. For a synchronous motor, the inverter "V" curve is the relation between
a) field current and power factor
b) field current and armature current
c) armature current and power factor
d) none of these
ans. a
5. In a synchronous motor , minimum armature current occurs at
a) zero power factor
b) unity power factor
c) lagging power factor
d) leading power factor
ans. b
6. A 3-ring synchronous converter supplying a dc 3-wire system must have the secondary of its transformer connected as
a) delta only
b) delta or star
c) zig-zag only
d) star or zig-zag
ans. c
7. The construction of synchronous motor is similar to
a) dc compound motor
b) slip ring induction motor
c) dc shunt motor
d) alternator
ans. d
8. The synchronous motor runs at
a) less than synchronous speed
b) synchronous speed
c) more than synchronous speed
d) none of these
ans. b
9. The synchronous motor runs on
a) 3-phase ac supply
b) 3-phase dc and ac supply
c) dc supply only
d) 3-phase ac and single phase ac
ans. b
10. If a synchronous motor is switched on to 3-phase supply with its rotor winding short circuited, it will
a) start
b) not start
c) start and continue to run as induction motor
d) start and continue to run as synchronous motor
ans. c
