Electrical Machines
In a single phase transformer the magnitude of leakage reactance is twice that of resistance of both primary and secondary. With secondary short circuited, the input power factor is

 1/√5
 1/3
 1/√2
 2/√5

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Electrical Machines
In DC machines, the interpoles are provided

  to make commutation spark less.
 to counteract the reactance voltage and the cross-magnetizi
  both (B) and (C).
 to counteract demagnetizing effect of armature mmf in commutating zone.

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

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