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

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

A synchronous motor installed at the receiving end substation operates with such an excitation that it takes power at lagging power factor. Now if the applied voltage of the synchronous motor goes down, the power factor of the synchronous motor will

A

remain same

B

go down

C

improve

D

none of the above

If the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will

A

stop

B

run as induction motor

C

function as static condenser

D

burn with dense smoke

After the starting winding of a single phase induction motor is disconnected from supply, it continues to run only on

A

running winding

B

rotor winding

C

field winding

D

compensating winding

If starting winding of a single-phase induction motor is left in the circuit, it will

A

run faster

B

spark at light loads

C

draw excessive current and overheat

D

run slower

The length of a rectangular field F is 3 km greater than the side of a square field M , and the width of field F is 3 km less then the side of field M. If the area of field M is m2 square km, what is the area of field F?

A

m2 +6

B

6

C

m2 - 6

D

m2 +9

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

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

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

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