Electrical Machines
Which of the following is not a necessary condition to be satisfied for synchronising an incoming alternator to an already operating alternator?

 same frequency
 same phase sequence
 same voltage magnitude
 same prime mover speed

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Electrical Machines
What is/are the necessary conditions for voltage build up in self excited generator?

 Field winding resistance should be less than critical resistance.
 Field winding should be properly connected to armature winding.
All of these
 Poles should contain residual flux.

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

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