Synchronous Motors
Damper winding in a synchronous motor________

Improve pf of the motor
Reduces windage losses
Increases hunting of the motor
Serves to start the motor

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Synchronous Motors
A synchronous motor connected to infinite bus-bars has at constant full load, 100% excitation and unity power factor. On changing the excitation only, the armature current will have

leading power factor with under-excitation
no change of power factor
lagging power factor with over-excitation
leading power factor with over-excitation

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