Electrical Machines
The demagnetising component of armature reaction in a DC generator

  reduces inter poles flux density.
  reduces generator emf.
  results in sparking trouble.
  increases armature speed.

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Electrical Machines
In synchronous generator, inverted V curve is drawn between

 field current on X-axis and armature current on Y-axis
 field current on Y-axis and power factor on X-axis
 field current on Y-axis and armature current on X-axis
 field current on X-axis and power factor on Y-axis

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Electrical Machines
Two of supply terminals to a 3 - Φ induction motor get interchanged during re-connection after normal maintenance. When switched on the supply, the motor will

  get heated and damaged.
  rotate in direction opposite to that before maintenance.
  rotate in the same direction as before maintenance.
  not start at all.

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Electrical Machines
Interpoles in a DC motor must be

 Shunt excited and should have the same polarity as that of the ahead main pole in the direction of rotation of armature.
 Series excited and should have the same polarity as that of the behind main pole in the direction of rotation of armature.
 Shunt excited and should have the same polarity as that of the behind main pole in the direction of rotation of armature.
 Series excited and should have the same polarity as that of the ahead main pole in the direction of rotation of armature.

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