Electrical Machines
Compensating windings are used in DC generators

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

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Electrical Machines
Flashing the field of DC generator means

  making the magnetic losses forces parallel.
  creating residual magnetism by a DC source.
 increasing flux density by adding extra turns of winding.
  neutralising residual magnetism.

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