Star-delta starting of motors is not possible in case of

Which one of the following is not necessarily the advantage of D.C. motors over A.C. motors?

A

Low cost

B

Wide speed range

C

Stability

D

High starting torque

Synchronous motors are generally not self-starting because

A

the direction of rotation is not fixed

B

the direction of instantaneous torque reverses after half cycle

C

startes cannot be used on these machines

D

starting winding is not provided on the machines

In _________ method of staging three phase induction motors the starting voltage is not reduced.

A

Autotransformer

B

Star-delta

C

Slip ring

D

Any of the above

A direct on line starter is used: for starting motors

A

Up to 5 H.P.

B

Up to 10 H.P.

C

Up to 15 H.P.

D

Up to 20 H.P.

________ need frequent starting and stopping of electric motors,

A

Paper mills

B

Grinding mills

C

Air-conditioners

D

Lifts and hoists

Which of the following motors is non-self starting ?

A

D.C. series motor

B

synchronous motor

C

Squirrel cage induction motor

D

Wound round induction motor

DOL starting of induction motors is usually restricted to

A

Low horsepower motors

B

Variable speed motors

C

High horsepower motors

D

High speed motors

Which of the following motors is inherently self starting ?

A

Split motor

B

Shaded-pole motor

C

Reluctance motor

D

None of these

Which of the following single-phase motors has relatively poor starting torque ?

A

Universal motor

B

Repulsion motor

C

Capacitor motor

D

All single phase motors have zero starting torque

Which of the following motors has highest starting torque ?

A

Repulsion motor

B

Shaped pole motor

C

Capacitor-start motor

D

Split-phase motor

Star-delta starting of motors is not possible in case of

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