MCQ on Single Phase Motor 1 - 18

1. In a split phase motor, the running winding should have
(a) high resistance and low inductance
(b) low resistance and high inductance✔
(c) high resistance as well as high inductance
(d) low resistance as well as low inductiance

2. If the capacitor of a single-phase motor is short-circuited
(a) the motor will not start✔
(b) the motor will run
(c) the motor will run in reverse direction
(d) the motor will run in the same direction at reduced r.p.m.

3. In capacitor start single-phase motors
(a) current in the starting winding leads the voltage✔
(b) current in the starting winding lags the voltage
(c) current in the starting winding is in phase with voltage in running winding
(d) none of the above

4. In a capacitor start and run motors the function of the running capacitor in series with the auxiliary winding is to
(a) improve power factor✔
(b) increase overload capacity
(c) reduce fluctuations in torque
(d) to improve torque

5. In a capacitor start motor, the phase displacement between starting and running winding can be nearly
(a) 10°
(b) 30°
(c) 60°
(d) 90°✔

6. In a split phase motor
(a) the starting winding is connected through a centrifugal switch✔
(b) the running winding is connected through a centrifugal switch
(c) both starting and running windings are connected through a centrifugal switch
(d) centrifugal switch is used to control supply voltage

7. The rotor developed by a single-phase motor at starting is
(a) more than i.he rated torque
(b) rated torque
(c) less than the rated torque
(d) zero✔

8. Which of the following motor will give relatively high starting torque ?
(a) Capacitor start motor✔
(b) Capacitor run motor
(c) Split phase motor
(d) Shaded pole motor

9. Which of the following motor will have relatively higher power factor ?
(a) Capacitor run motor✔
(b) Shaded pole motor
(c) Capacitor start motor
(d) Split phase motor

10. In a shaded pole motor, the shading coil usually consist of
(a) a single turn of heavy wire which is in parallel with running winding
(b) a single turn of heavy copper wire which is short-circuited and carries only induced current✔
(c) a multilayer fine gauge copper wire in parallel with running winding
(d) none of the above

11. In a shaded pole single-phase motor, the revolving field is produced by the use of
(a) inductor
(b) capacitor
(c) resistor
(d) shading coils✔

12. A centrifugal switch is used to dis- connect ‘starting winding when motor has
(a) run for about 1 minute
(b) run for about 5 minutes
(c) picked up about 50 to 70 per cent of rated speed✔
(d) picked up about 10 to 25 per cent of rated speed

13. If a particular application needs high speed and high starting torque, then which of the following motor will be preferred ?
(a) Universal motor✔
(b) Shaded pole type motor
(c) Capacitor start motor
(d) Capacitor start and run motor

14. The value of starting capacitor of a fractional horse power motor will be
(a) 100 uF
(6) 200 uF
(c) 300 uF✔
(d) 400 uF

15. In repulsion motor direction of rotation of motor
(a) is opposite to that of brush shift
(b) is the same as that of brush shift✔
(c) is independent of brush shift

16. In a single phase motor the centrifugal switch
(a) disconnects auxiliary winding of the motor✔
(b) disconnects main winding of the motor
(c) reconnects the main winding the motor
(d) reconnects the auxiliary winding of the motor

17. The running winding of a single phase motor on testing with meggar is found to be ground. Most probable location of the ground will be
(a) at the end connections
(b) at the end terminals
(c) anywhere on the winding inside a slot
(d) at the slot edge where coil enters or comes out of the slot✔

18. A capacitor-start single phase induction motor is switched on to supply with its capacitor replaced by an inductor of equivalent reactance value. It will
(a) start and then stop
(b) start and run slowly
(c) start and run at rated
(d) All of above✔