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 prime mover speed
 same voltage magnitude
 same frequency
 same phase sequence

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Electrical Machines
Armature reaction in a DC machine

 is in the same direction as the main poles.
 makes an angle with the main pole axis which is load dependent.
 is in direct opposition to the main poles.
  makes an angle of 90° with the main pole axis.

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Electrical Machines
A dc shunt generator, when commissioned after a major repair of the field system, failed to build Up voltage. It was because

 there was a break in the armature circuit
 field system lost residual magnetism
 field winding was wrongly connected
 field resistance was higher than critical resistance

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