Under which of the following conditions is a dc motor provided with compensating winding used ? 1. Wide range of speed control above normal 2. Wide range of steady load variation with no speed control 3.Wide range of rapid variation in load Select the correct answer using the codes given below : Codes :

Electrical Machines
Under which of the following conditions is a dc motor provided with compensating winding used ? 1. Wide range of speed control above normal 2. Wide range of steady load variation with no speed control 3.Wide range of rapid variation in load Select the correct answer using the codes given below : Codes :

1 and 3

1, 2 and 3

2 and 3

1 and 2

1 and 3

1, 2 and 3

2 and 3

1 and 2

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The emf induced in a conductor rotating in a bipolar field is

DC.

None of these

AC.

both of above.

DC.

None of these

AC.

both of above.

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Electrical Machines
Oil is provided in an oil filled transformer for

lubrication.

insulating.

cooling.

both cooling and insulation.

lubrication.

insulating.

cooling.

both cooling and insulation.

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Electrical Machines
Which of these types of motor is used in elevators?

None of these.

DC series motor.

DC shunt motor.

DC compound motor.

None of these.

DC series motor.

DC shunt motor.

DC compound motor.

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Electrical Machines
In a dc generator operating on load with its brushes on the geometrical neutral axis (GNA), the magnetic neutral axis (MNA) is shifted in the direction of rotation. Now, if the brushes are given a lead of 90° (electrical), then the MNA will

coincide with the GNA

shift forward by 90°

shift forward by more than 90°

shift forward by less than 90°

coincide with the GNA

shift forward by 90°

shift forward by more than 90°

shift forward by less than 90°

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Electrical Machines
If the armature electric current is increased to double its previous value, and the time of commutation is halved, how will the reactance voltage vary?

It will be doubled.

It will becomes four times.

It will remain the same.

It will be halved.

It will be doubled.

It will becomes four times.

It will remain the same.

It will be halved.

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Electrical Machines

Electrical Machines The emf induced in a conductor rotating in a bipolar field is

Electrical Machines Oil is provided in an oil filled transformer for

Electrical Machines Which of these types of motor is used in elevators?

Electrical Machines In a dc generator operating on load with its brushes on the geometrical neutral axis (GNA), the magnetic neutral axis (MNA) is shifted in the direction of rotation. Now, if the brushes are given a lead of 90° (electrical), then the MNA will

Electrical Machines If the armature electric current is increased to double its previous value, and the time of commutation is halved, how will the reactance voltage vary?

Electrical Machines
The emf induced in a conductor rotating in a bipolar field is

Electrical Machines
Oil is provided in an oil filled transformer for

Electrical Machines
Which of these types of motor is used in elevators?

Electrical Machines
In a dc generator operating on load with its brushes on the geometrical neutral axis (GNA), the magnetic neutral axis (MNA) is shifted in the direction of rotation. Now, if the brushes are given a lead of 90° (electrical), then the MNA will

Electrical Machines
If the armature electric current is increased to double its previous value, and the time of commutation is halved, how will the reactance voltage vary?