Electrical Machines
In field flux method speed control of DC Motor is

 constant hp drive below the base speed.
 constant power drive above base speed.
 constant torque drive above the base speed.
 constant torque drive below the base speed.

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Electrical Machines
An alternator is feeding an infinite busbar. Its prime mover is suddenly shutdown. The alternator will

 come to stand still.
 start working as induction motor.
 continue to work as alternator but the direction of rotation will reverse.
 continue to work as synchronous motor with same direction of rotation.

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Electrical Machines
Which of the following factors improve commutation in a dc machine ? 1. High contact resistance of brushes 2. High inductance of the coils undergoing commutation 3. Shifting of brushes in the direction of rotation for a generator and in the opposite direction For a motor 4. Narrow width for the commutation bars Select the correct answer using the codes given below : Codes :

 1, 2 and 4
 1, 2, and 3
 2, 3 and 4
 1 and 3

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