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

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

(I) Even at no load a large 3-phase squirrel- cage induction motor is started at reduced voltage than rated. (II) If a large 3–phase squirrel-cage induction motor with no load is started at full voltage, it will be damaged.

A

I is true, II is false

B

I is true and II is also true

C

I is false, II is true

D

I and II are false

The advantage of the double squirrel cage induction motor over a single cage rotor is that its _______

A

Efficiency is higher

B

Power factor is higher

C

Slip is larger

D

Starting current is lower

The great advantage of the double squirrel-cage induction motor over single cage rotor is that its _________

A

efficiency is higher

B

power factor is higher

C

slip is larger

D

starting current is lower

Variable speed motors especially N.E.M.A. B squirrel cage A.C. induction motors might be operated by __.

A

Variable frequency drive

B

Direct current

C

2 horsepower

D

756 horsepower

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

Wound rotor induction motor has better ________ characteristics than Squirrel cage induction motor.

A

Starting

B

Running

C

Modified

D

Quasi-state

Relatively a squirrel-cage induction motor is advantageous over wound rotor type induction motor of identical rating due to ___________

A

less conductor material used.

B

lower leakage flux

C

ruggedness

D

all of the mentioned

Rotor rheostat speed control method can be used for controlling the speed of squirrel cage motors.

A

True

B

False

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

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