Electrical Machines
The synchronous reactance( Xs) is the

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

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Electrical Machines
For a given torque, reducing divertor resistance of a DC series motor

  Increase in speed but armature currnet remains the same.
  Decrease in speed but armature current remains the same.
  Increase in speed demanding more armature current.
  Decrease in speed demanding less armature current.

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