Electrical Machines
Resistance commutation is used generally in case of

 DC machines above 10 kW.
None of these
 DC machines bellow 5 kW.
  fractional kW DC machines.

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

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

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

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

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