Short-circuit test on an induction motor cannot be used to determine

A wound rotor induction motor is preferred, as compared to squirrel cage induction motor, when major consideration is

A

Slop speed operation

B

High starting torque

C

Low windage losses

D

All of the above

The circle diagram for an induction motor cannot be used to determine

A

Efficiency

B

Power factor

C

Frequency

D

Output

While starting a synchronous motor by induction motor action, field winding is usually

A

connected to D.C. supply

B

short-circuited by low resistance

C

kept open-circuited

D

none of the above

A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because

A

synchronous motor has no slip

B

stator supply is not required to produce magnetic field

C

mechanical load on the rotor remains constant

D

synchronous motor has large airgap

While starting a salient pole synchronous motor by induction motor action and connecting field discharge resistance across field, starting and accelerting torque is produced by

A

induction motor torque in field winding

B

induction motor torque in damper winding

C

eddy current and hysteresis torque in pole faces

D

reHetance motor torque due to saliency of the rotor

E

all of the above methods

Slip ring motor is preferred over squirrel cage induction motor where

A

High starting torque is required

B

Load torque is heavy

C

Heavy pull out torque is required

D

All of the above

The power factor of a synchronous motor is better than that of induction motor because

A

stator supply is relieved of responsibility of producing magnetic field

B

mechanical load on the motor can be adjusted

C

synchronous motor runs at synchronous speed

D

synchronous motor has large air gap

An important advantage of a synchronous motor over wound round induction motor is that

A

its power factor may be varied at will

B

its speed is independent of supply frequency

C

its speed may be controlled more easily

D

none of the above

Flywheel is used with D.C. compound motor to reduce the peak demand by the motor, compound motor will have to be

A

Level compounded

B

Under compounded

C

Cumulatively compounded

D

Differentially compounded

Of the 120 households in an area, 55 have cars, 35 have motor bikes, and 20 have both cars and motor bikes. How many of the households in the area have neither cares nor motor bikes?

A

110

B

90

C

50

D

30

Short-circuit test on an induction motor cannot be used to determine

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