Generator Rotor wedges,Retaining rings & Ventilation and cooling
Rotor wedges:-
Rotor winding is held in position by single/double dovetail shaped wedges made of non-magnetic material for two pole generators. This enables the winding to withstand high centrifugal force in operation and act as a damper circuit for current induced in rotor during in advert ant asynchronous operation these wedges help to have a good heat dissipation. Thus maintaining temp within escapable limits.
In the case of 1500r.p.m Generators wedges of rectangular sections of glass material with resin absorption during impregnation are employed with a result in firm gripping with laminated rotor core and have the high mechanical strength after impregnation.
`Rotor winding overhang of two pole Turbo generators are fitted with non-magnetic high strength steel retaining rings with preventing the movement of rotor winding overhang due to centrifugal force in operation this retaining rings are shrunk fitted on the rotor body at one end and are either floating or rigidity fixed at the other end.
Turbo generators are designed with the following ventilation system.
Closed circuit is cooling with water/ air coolers mounted on the pit.
Closed circuit Hydrogen cooling with water/ Hydrogen coolers mounted axially on the stator frame.
The fan design usually consists of axial fans either of cast aluminium with integral fan blades or forged and machined aluminium alloy blades screwed to the rotor. In the case of 1500r.p.m Generator ’s fabricated radial fans are provided.