Deck 1: Single-Phase Motor

Question 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

Answer 1

low resistance and high inductance

Question 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.

Answer 2

the motor will not start

Question 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

Answer 3

current in the starting winding leads the voltage

Question 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

Question 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°

Question 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

Question 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

Question 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

Question 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

Question 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

Question 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

Question 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

Question 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

Question 14

The value of starting capacitor of a fractional horse power motor will be

A)100 uF
B)200 uF
C)300 uF
D)400 uF

Question 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
D)none of the above

Question 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

Question 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

Question 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 speed
D)not start at all

Question 19

Which of the following motors is used in mixies ?

A)Repulsion motor
B)Reluctance motor
C)Hysteresis motor
D)Universal motor

Question 20

Which of the following motors is inherently self starting ?

A)Split motor
B)Shaded-pole motor
C)Reluctance motor
D)None of these

Question 21

The direction of rotation of an hysteresis motor is determined by

A)interchanging the supply leads
B)position of shaded pole with respect to main pole
C)retentivity of the rotor material
D)none of these

Question 22

Burning out of windings is due to

A)short circuited capacitor
B)capacitor value hiving changed
C)open circuiting of capacitor
D)none of the above

Question 23

Direction of rotation of a split phase motor can be reversed by reversing the connection of

A)running winding only
B)starting winding only
C)either (a) or (b)
D)both (a) and (b)

Question 24

Short-circuiter is used in

A)repulsion induction motor
B)repulsion motor
C)repulsion start induction run motor
D)none of the above

Question 25

The range of efficiency for shaded pole motors is

A)95% to 99%
B)80% to 90%
C)50% to 75%
D)5% to 35%