In squirrel cage induction motors which of the following methods of starting cannot be used?

In three-phase squirrel-cage induction motors

A

Rotor conductor ends are short-circuited through slip rings

B

Rotor conductors are short-circuited through end rings

C

Rotor conductors are kept open

D

Rotor conductors are connected to insulation

In squirrel cage induction motors, the rotor slots are usually given slight skew in order to

A

Reduce windage losses

B

Reduce eddy currents

C

Reduce accumulation of dirt and dust

D

Reduce magnetic hum

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

The starting torque of a squirrel-cage induction motor is

A

low

B

negligible

C

same as full-load torque

D

slightly more than full-load torque

Which of the following methods is easily applicable to control the speed of the squirrel-cage induction motor?

A

By changing the number of stator poles

B

Rotor rheostat control

C

By operating two motors in cascade

D

By injecting e.m.f. in the rotor circuit

The speed of a squirrel-cage induction motor can be controlled by all of the following except

A

Changing supply frequency

B

Changing number of poles

C

Changing winding resistance

D

Reducing supply voltage

A double squirrel-cage induction motor has

A

Two rotors moving in opposite direction

B

Two parallel windings in stator

C

Two parallel windings in rotor

D

Two series windings in stator

When the equivalent circuit diagram of double squirrel-cage induction motor is constructed the two cages can be considered

A

In series

B

In parallel

C

In series-parallel

D

In parallel with stator

The number of slip rings on a squirrel cage induction motor is usually

A

Two

B

Three

C

Four

D

None

A squirrel cage induction motor is not selected when

A

Initial cost is the main consideration

B

Maintenance cost is to be kept low

C

Higher starting torque is the main consideration

D

All above considerations are involved

In squirrel cage induction motors which of the following methods of starting cannot be used?

Related Questions