The vafcie of transformation ratio of an induction motor can be found by

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

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

The power scale of circle diagram of an induction motor can be found from

A

Stator resistance test

B

No-load test only

C

Short-circuit test only

D

None of the above

The complete circle diagram of induction motor can be drawn with the help of data found from

A

No-load test

B

Blocked rotor test

C

Stator resistance test

D

All of the above

By looking at which part of the motor, it can be easily confirmed that a particular motor is D.C. motor?

A

Frame

B

Shaft

C

Commutator

D

Stator

The vafcie of transformation ratio of an induction motor can be found by

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