Damper ring of turbo-generators have some duties such as maintaining synchronism (damping the oscillations), decreasing the losses on the surface of the rotor due to pulsating fields in the air gap, start-up performance.
The question is how can it be designed geometrically?
In reference books, the geometry of rotor wedges (cross-section of the active part of dampers) are pertained to the cross-section of armature winding. is is said, the cross-section of rotor wedges must be something between 20 to 30 percent of the cross-section of the armature winding.
Is there other hints on this?