Electrical Machines
In DC generator, armature reaction refers to what?

None of these
 Effect of field flux on the armature flux.
  Effect of armature flux on the main field flux.
 Effect of armature flux on the load.

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Electrical Machines
A dc shunt generator, when driven without any excitation, showed an open circuit voltage of 12 V. When the field winding was excited, the voltage dropped to zero. It happened because

 field resistance was higher than critical resistance
 there was a break in the armature circuit
 field winding was wrongly connected
 there was no residual magnetism in the field circuit

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Electrical Machines
In large sized DC machines the compensating windings are provided to

 compensate for the decrease in speed due to increase of load.
  neutralize voltage induced in coil due to fluctuation of l
None of these
 reduce eddy current losses by providing local short circuits.

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

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

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