DC MOTORS QUIZ

The back emf in a dc motor ______

None of the listed here

Aids the applied voltage

Opposes the applied voltage

Aids the armature current

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The speed of a series motor at no load is

4000 rpm

1000 rpm

2000 rpm

Infinity

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Armature reaction in dc motor is increased

When the armature current increases

By interpoles

When the field current increases

When the armature current decreases

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The main disadvantage of the Ward-Leonard control method is

High maintenance cost

High initial cost

Low efficiency at high loads

All of these

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By looking at which part of the motor, it can be easily confirmed that a particular motor is D.C. motor?

Commutator

Shaft

Stator

Frame

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In a dc machines the residual magnetism is of the order of

20 to 25 percent

10 to 15 percent

50 to 75 percent

2 to 3 percent

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In a dc compound machine,

Both play equally dominant role

Shunt field winding plays dominant role

Either can play dominant role

Series field winding plays dominant role

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The plugging gives the

Zero torque braking

Smallest torque braking

Highest torque braking

None of the listed here

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No load speed of which of the following motor will be highest?

Series motor

Cummulative compounded motor

Differentially compounded motor

Shunt motor

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A direct on line starter is used for starting motors

Upto 20 HP

Upto 10 HP

Upto 5 HP

Upto 15 HP

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