Electrical Machines
The oscillation in a synchronous motor can be damped out by

  oscillation cannot be damped.
  maintaining constant excitation.
  providing damper bars in the rotor pole faces.
  running the motor on leading power factors.

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Electrical Machines
The mmf produced by rotor currents of a 3 - Φ induction motor

  rotates at synchronous speed with respect to rotor.
  rotates at the speed of rotor in the air gap.
  is at standstill with respect to stator mmf.
  rotates at slip speed with respect to stator mmf.

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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

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

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Electrical Machines
The results of a slip test for determining direct axis (Xd) and quadrature axis (Xq) reactances of a star connected salient pole alternator are given below Phase values: Vmax = 108 V ; Vmin = 96 V Imax = 12 A ; Imin = 10 A Hence the two reactances will be

 Xd = 9Ω and Xq = 9.6Ω
 Xd = 9.6Ω and Xq = 9Ω
 Xd = 10.8Ω and Xq = 8Ω
 Xd = 8Ω and Xq = 10.8Ω

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Electrical Machines
For a given torque, reducing diverter resistance of a DC series motor causes

 decrease in speed but armature current remains the same.
 decrease in speed demanding less armature current.
 increase in speed but armature currnet remains the same.
 increase in speed demanding more armature current.

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