Insertion of resistance in the rotor of an induction motor to develop a given torque

Insertion of resistance in the rotcir of an induction motor to develop a given torque

A

decreases the rotor current

B

increases the rotor current

C

rotor current becomes zero

D

rotor current rernains same

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 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

The maximum torque which a synchronous motor will develop at rest for any angular position of the rotor, at rated stator supply voltage and frequency, is known as

A

locked-rotor torque

B

synchronous torque

C

pull up torque

D

reluctance torque

The torque of a rotor in an induction motor under running condition is maximum

A

At the unit value of slip

B

At the zero value of slip

C

At the value of the slip which makes rotor reactance per phase equal to the resistance per phase

D

At the value of the slip which makes the rotor reactance half of the rotor

Insertion of resistance in the stator of an induction motor

A

Increases the load torque

B

Decreases the starting torque

C

Increases the starting torque

D

None of the above

The power input to an induction motor is 50 kW when it is running at 4% slip. If the stator resistance and core losses are neglected, the rotor copper loss is

A

30 kW

B

20 kW

C

2 kW

D

4 kW

In the squirrel-cage induction motor the rotor slots are usually given slight skew

A

To reduce the magnetic hum and locking tendency of the rotor

B

To increase the tensile strength of the rotor bars

C

To ensure easy fabrication

D

None of the above

In an induction motor the relationship between stator slots and rotor slots is that

A

Stator slots are equal to rotor slots

B

Stator slots are exact multiple of rotor slots

C

Stator slots are not exact multiple of rotor slots

D

None of the above

What will happen if the relative speed between the rotating flux of stator and rotor of the induction motor is zero?

A

The slip of the motor will be 5%

B

The rotor will not run

C

The rotor will run at very high speed

D

The torque produced will be very large

Insertion of resistance in the rotor of an induction motor to develop a given torque

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