Starters are used with D.C. motors because

A coach must choose five starters from a team of 12 players. How many different ways canthe coach choose the starters ?

A

569

B

729

C

625

D

769

Starters are required in the induction motor because __________

A

of high starting current

B

they are not self starting

C

torque produced is very low at starting to overcome inertia

D

all of the mentioned

In 4-point starters the resistance is added in series with NVC because __________________

A

To increase field current

B

To increase armature current

C

To limit the NVC current

D

To limit armature current

Which of the following materials is used in the manufacture of resistance grids to be used in the starters of largemotors ?

A

Copper

B

Aluminium

C

Steel

D

Cast-iron

The auto-starters (using three auto transformers) can be used to start cage induction motor of the following type

A

Star connected only

B

Delta connected only

C

Both (A) and (B)

D

None of the above

The shunt motor starters that can be used is/are ___________

A

3-point and 4-point starter

B

5-point starter

C

4-point starter

D

5-point and 3-point starter

Why starters are required in a DC motor?

A

Back emf of these motors is zero initially

B

These motors are not self-starting

C

These motors have high starting torque

D

To restrict armature current as there is no back emf at starting

In modern starters, the pole shoes are replaced with which component?

A

Titanium coil

B

Carbon brushes

C

Permanent magnet

D

Electro-magnet

Assertion (A): DC servomotors are more commonly used in armature controlled mode than field controlled mode. Reason (R): Armature controlled Dc motors have higher starting torque than fiels controlled motors.

A

Both A and R are true and R is the correct explanation of A

B

Both A and R are true but R is not correct explanation of A

C

A is true but R is false

D

A is false but R is true

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

Starters are used with D.C. motors because

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