Practice Polyphase Induction Motors Multiple Choice Questions Quiz-2 - MCQGeeks.com

Q.1

An induction motor is identical to

D.C. compound motor
D.C. series motor
Synchronous motor
Asynchronous motor

Q.2

In a three-phase induction motor

Power factor at starting is high as compared to that while running
Power factor at starting is low as compared to that while running
Power factor at starting in the same as that while running
None of these

Q.3

In the circle diagram for induction motor, the diameter of the circle represents

Slip
Rotor current
Running torque
Line voltage

Q.4

Insertion of resistance in the stator of an induction motor

Increases the load torque
Decreases the starting torque
Increases the starting torque
None of the above

Q.5

In a star-delta starter of an induction motor

Resistance is inserted in the stator
Reduced voltage is applied to the stator
Resistance is inserted in the rotor
Applied voltage per stator phase is 57.7% of the line voltage

Q.6

Slip ring motor is preferred over squirrel cage induction motor where

High starting torque is required
Load torque is heavy
Heavy pull out torque is required
All of the above

Q.7

A change of 4% of supply voltage to an induction motor will produce a change of approximately

4% in the rotor torque
8% in the rotor torque
12% in the rotor torque
16% in the rotor torque

Q.8

The crawling in the induction motor is caused by

Low voltage supply
High loads
Harmonics developed in the motor
Improper design of the machine

Q.9

In case the air gap in an induction motor is increased

The magnetizing current of the rotor will decrease
The power factor will decrease
Speed of motor will increase
The windage losses will increase

Q.10

Temperature of the stator winding of a three phase induction motor is obtained by

Resistance rise method
Thermometer method
Embedded temperature method
All above methods

Q.11

In case of the induction motors the torque is

Inversely proportional to (V-slip)
Directly proportional to (slip)2
Inversely proportional to slip
Directly proportional to slip

Q.12

Slip ring motor is recommended where

Speed control is required
Frequent starting, stopping and reversing is required
High starting torque is needed
All above features are required

Q.13

If a 3-phase supply is given to the stator and rotor is short circuited rotor will move

In the opposite direction as the direction of the rotating field
In the same direction as the direction of the field
In any direction depending upon phase sequence of supply
None of these

Q.14

The shaft of an induction motor is made of

High speed steel
Stainless steel
Carbon steel
Cast iron

Q.15

The number of slip rings on a squirrel cage induction motor is usually

Two
Three
Four
None

Q.16

In a squirrel cage motor the induced e.m.f. is

Dependent on the shaft loading
Dependent on the number of slots
Slip times the stand still e.m.f. induced in the rotor
None of the above

Q.17

Size of a high speed motor as compared to low speed motor for the same H.P. will be

Bigger
Smaller
Same
Any of the above

Q.18

In an induction motor, no-load the slip is generally

Less than 1 %
1.5 %
2 %
4 %

Q.19

The shape of the torque/slip curve of induction motor is

Parabola
Hyperbola
Rectangular parabola
Straight line

Q.20

The auto-starters (using three auto transformers) can be used to start cage induction motor of the following type

Star connected only
Delta connected only
Both (A) and (B)
None of the above

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