Electrical Machine - II (3150910) MCQs

MCQs of Single-Phase Induction Motors

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1.

In a split-phase motor, the running winding must have _____________________ to ensure ________________ .

(a)

Low resistance and Low inductance,         High operating PF
(b)

Low resistance and high inductance,          High operating Efficiency
(c)

High resistance and High inductance,          High operating Efficiency
(d)

High resistance and low inductance,         High operating PF
Answer:

Option (b)

2.

What happens if the capacitor of a single-phase induction motor gets short-circuited / Open-circuited?

(a)

The motor will run in a reverse direction
(b)

The motor will run in the same direction at reduced speed
(c)

The motor will not start
(d)

None of these 
Answer:

Option (c)

3.

In a split-phase motor

(a)

The running winding is connected through a centrifugal switch
(b)

The starting winding is connected through a centrifugal switch
(c)

Centrifugal switch is used to control supply voltage
(d)

Both starting and running windings are connected through a centrifugal switch
Answer:

Option (b)

4.

The torque developed by a single-phase motor at starting is

(a)

equal to the rated torque
(b)

greater than the rated torque
(c)

less than the rated torque
(d)

zero
Answer:

Option (d)

5.

What is the role of a capacitor connected in series with the auxiliary winding in Permanent Split Capacitor (PSC)  1-Φ Induction Motor?

(a)

Produce Starting torque & Improve running power factor  
(b)

Increase motor capacity
(c)

Reduce fluctuations in torque
(d)

Decrease voltage fluctuation 
Answer:

Option (a)

6.

From the following single-phase induction motor, Which motor has relatively higher power factor?

(a)

Resistance Split-phase
(b)

Capacitor Start Split-phase
(c)

Permanent Split Capacitor (PSC)
(d)

Capacitor Start Capacitor Run (Two Value capacitor)
Answer:

Option (c)

7.

On __________ of the rated speed of the motor, the centrifugal switch disconnect the _________ winding from supply.

(a)

10 – 20%,     running
(b)

20 – 30%,     starting
(c)

30 – 40%,     running
(d)

70 – 80%,     starting
Answer:

Option (d)

8.

In repulsion motor, the direction of rotation of the motor is determined by 

(a)

the position of the brushes with respect to the magnetic field of the rotor
(b)

the position of the brushes with respect to the magnetic field of the stator
(c)

the position of the brushes with respect to the supply connection
(d)

Could be anything, we can not predict 
Answer:

Option (b)

9.

In repulsion motor, If the brushes are shifted clockwise from the main magnetic axis, the motor will _______________ .

 

(a)

rotate in an anticlockwise direction. 
(b)

rotate in a clockwise direction. 
(c)

remain unchanged (direction does not depend on brushes shifting)
(d)

stop
Answer:

Option (b)

10.

________________ motor will be preferred for require high-speed and high starting torque application.

(a)

Universal Motor
(b)

Capacitor run motor
(c)

Capacitor start motor
(d)

Shaded pole motor
Answer:

Option (a)

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