Which of the following losses, in a synchronous motor, does not vary with load?

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

A synchronous motor is running on a load with normal excitation. Now if the load on the motor is increased

A

power factor as well as armature current will decrease

B

power factor as well as armature current will increase

C

power factor will increase but armature current will decrease

D

power factor will decrease and armature current will increase

In case of a reluctance motor, when the load is increased so that it cannot maintain synchronous speed the motor will

A

Become unstable

B

Draw excessive armature current and may burn out

C

Fall out of synchronism and come to stand still

D

Run as induction motor

As the load is applied to a synchronous motor, the motor takes more armature current because

A

The increased load has to take more current

B

The rotor by shifting its phase backward causes motor to take more current

C

The back e.m.f. decreases causing an increase in motor current

D

The rotor strengthens the rotating field causing more motor current

Which of the following losses is not dissipated by the stator core surface in a synchronous motor ?

A

Eddy current losses in the conductors

B

Iron losses in the stator

C

Copper losses in the slot portion of the conductors

D

Windage losses

A synchronous motor can be used as a synchronous capacitor when it is

A

under-loaded

B

over-loaded

C

under-excited

D

over-excited

A synchronous motor can develop synchronous torque

A

when under loaded

B

while over-excited

C

only at synchronous speed

D

below or above synchronous speed

A synchronous motor which works on a leading power factor and does not drive a mechanical load is called as

A

static condenser

B

condenser

C

synchronous condenser

D

none 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

Which of the following losses, in a synchronous motor, does not vary with load?

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