Electrical Machines
In a synchronous motor when the rotor speed exceeds the synchronous speed during hunting

  negative sequence currents are generated.
  the damper bars develop induction motor torque.
  the damper bars develop induction generator torque.
  the damper bars develop synchronous motor torque.

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Electrical Machines
In a loaded DC generator, if the brushes are given a shift from the interpolar axis in the direction of rotation, then the commutation will

 deteriorate with fall of terminal voltage.
 improve with fall of terminal voltage.
 deteriorate with rise in terminal voltage.
 improve with rise in terminal voltage.

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Electrical Machines
Ward-Leonard system for controlling the speed of a DC motor is used where

 The accuracy in speed control is required.
 The speed in both the direction is required.
 Very fine speed control over the whole range from zero to normal speed is required.
 All of above.

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