Electrical Machines
A 3-φ alternator has negligible stator resistance. A short circuit test is conducted on this alternator. At a particular speed, a field current of If1 is required to drive the rated armature current. If the speed of the alternator is reduced to half, the field current required to maintain rated armature current

 Would be equal to If1/2.
 Would be equal to If1.
  Cannot be predicted due to insufficient data.
 Woud be equal to 2If1.

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

  Increase in speed but armature currnet remains the same.
  Increase in speed demanding more armature current.
  Decrease in speed demanding less armature current.
  Decrease in speed but armature current remains the same.

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Electrical Machines
What will happen if the the supply terminals are reversed in case of a DC shunt motor?

 The motor will run much faster in the same direction.
 The motor will stop.
 The motor will run at its normal speed in the same direction as before.
 The motor will run in reverse direction.

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