Electrical Machines
For satisfactory parallel operation of two transformers which of the following conditions is most essential,

  polarities of all transformers must be same.
 voltage ratio of all transformers must be same.
 percentage impedance of all transformers must be same.
 MVA rating of all transformer inversely proportional to impedance.

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Electrical Machines
In a synchronous motor when the rotor speed exceeds the synchronous speed during hunting

  the damper bars develop induction motor torque.
  the damper bars develop induction generator torque.
  the damper bars develop synchronous motor torque.
  negative sequence currents are generated.

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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

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

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