Electrical Machines
The mmf produced by rotor currents of a 3 - Φ induction motor

  rotates at synchronous speed with respect to rotor.
  rotates at the speed of rotor in the air gap.
  is at standstill with respect to stator mmf.
  rotates at slip speed with respect to stator mmf.

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Electrical Machines
Compensating windings are used in DC generators

  to provide path for the circulation of cooling air.
  mainly to reduce the eddy currents by providing local short circuit.
None of these
  to neutralize the cross magnetizing effect of the armature reaction.

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Electrical Machines
The synchronous reactance( Xs) is the

 reactance due to leakage flux
 combined reactance due to armature reaction and leakage flux
 reactance due to armature reaction of the machine
 reactance either due to armature reaction or leakage flux

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