How damper winding provides smooth starting to synchronous machine.

The damper winding (also known as ammortisseur) is mostly used in synchronous machine- in stator of synchronous generator and rotor of synchronous motor. It provides some specific advantage to synchronous machines like – smooth starting and compensating the transient effect or unbalanced condition.

The rotor of induction machine is mostly of squirrel cage type which is short circuited thus provides high current in start up.

Damper winding in synchronous machine is placed in the coil slots and short circuited. Thus Damper winding provides the same effect as the squirrel cage winding rotor does in case of induction motor.

Position of damper winding:

Damper winding is placed in the slots at the surface of pole shoes in salient pole machines and in in non-salient pole machine it is placed in the same slots with magnetizing windings.

damper winding in salient pole machine
Damper winding in salient pole machine

Function of damper winding in synchronous machine:

1.Self starting of synchronous machine: The core concept is that damper winding being short circuited carry high current, creates magnetic flux like as induction machine. Thus there is pulling in or better torque in starting. This is done in the moment of starting when synchronous machine is not yet reached in synchronism. Because synchronous machine before synchronism has the characteristics of an induction machine as there is relative motion between rotor and stator. When the machine reached in synchronism, there will be no current in damper winding as there is no relative motion between rotor and stator.

2.Compensation of transients by damping the rotational fluctuation (hunting) caused by unbalanced loading, torque etc. Whenever the synchronous machine is pulled out from synchronism – as there will be relative motion between the rotor and stator, the damper winding will provide flux which will compensate the transient effect and machine will return back to synchronism.

Turbo Generator usually don’t have damper windings,as their solid field poles functions as damper.But they might use damper windings for synchronization purpose.

damper winding of electrical machine
Damper windings are copper bar slotted in pole shoes of electrical machine.The dampers are short circuited at both ends by heavy copper rings.

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