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 winding was wrongly connected
 field system lost residual magnetism
 field resistance was higher than critical resistance

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Electrical Machines
In a star - delta starting of an IM

  resistance is inserted in the rotor.
  line voltage is 57.7 % of stator voltage.
  reduced voltage is applied to the stator.
  applied voltage per stator phase is 57.7 % of a line volt

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