Centrifugal switch disconnects the auxiliary winding of the motor at about ____ percent of synchronous speed

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

When the main switch of the house is put off it disconnects the

A

Live wire only

B

Live wire and the earth wire

C

Live wire and the neutral wire

D

Earth wire and the neutral wire

A centrifugal switch is used to disconnect starting winding when motor has

A

run for about 1 minute

B

run for about 5 minutes

C

picked up about 50 to 70 per cent of rated speed

D

picked up about 10 to 25 per cent of rated speed

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

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

In split-phase motor auxiliary winding is of

A

thick wire placed at the bottom of the slots

B

thick wire placed at the top of the slots

C

thin wire placed at the top of the slots

D

thin wire placed at the bottom of the slots

A partial auxiliary view is used to show only the __________ in the auxiliary view.

A

Projected inclined plane

B

The projected top view

C

The projected side view

D

None of the above

When the rotor speed, in a synchronous machine, becomes more than the synchronous speed during hunting, the damper bars develop

A

inductor motor torque

B

induction generator torque

C

synchronous motor torque

D

d.c. motor toque

In a synchronous motor, the damping winding is generally used to

A

prevent hunting and provide the starting torque

B

reduce the eddy currents

C

provide starting torque only

D

reduce noise level

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

Centrifugal switch disconnects the auxiliary winding of the motor at about ____ percent of synchronous speed

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