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

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

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Electrical Machines
Two of supply terminals to a 3 - Φ induction motor get interchanged during re-connection after normal maintenance. When switched on the supply, the motor will

  not start at all.
  rotate in the same direction as before maintenance.
  rotate in direction opposite to that before maintenance.
  get heated and damaged.

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