Integrated End-Winding Ring Support For Water-Cooled Stator Winding Design Features, Analysis, Test Results and Experience

An integrated stator end-winding support design which differs from conventional support systems is described in this paper. This design is called "Ringbloc system" and features stiff end-winding support by forming a solid, resin-filled end-winding arc with the bar ends bolted to a funnel-shaped backing ring. The backing ring encircles the end winding and is mounted on heavy brackets that allow only movement in the axial direction from thermal expansion. The short-circuit analysis outlined reveals an approximately tenfold reduction of end-winding deflections and stresses due to the stiffness of the composite end-winding arc and backing ring structure. The design is described in detail and considerable information from factory and field tests is presented. The paper also provides information on the operating experience with two-pole and four-pole generators up to ratings of 1530 MVA demonstrating the effectiveness of the Ringbloc system.