Improved groundwall insulation system for air cooled generators

A new insulation system has been developed for coils that are used in air cooled generator stator windings. The power density of these air cooled generators can be increased through better thermal performance of the stator coil insulation. The approach taken to achieve better thermal performance is to reduce the groundwall insulation thickness and at the same time improve the coil's dielectric parameters. This paper describes a new air cooled stator coil insulation design that incorporate design improvements in three major areas of the coil's insulation components. These are the groundwall insulation, the Roebel filler material, and the external corona suppression. Each of these improvements are reviewed with respect to the role they play in the overall dielectric performance of the new coil design.