Abstract: In a dynamoelectric machine, the rotor comprises a solid steel drum formed with axially extending channels which carry electrically-conductive windings. These windings are electrically insulated from the rotor body by so-called slot insulation. The present invention proposes an integrally formed composite insulation comprising aramid paper slot armor and an epoxy-glass sub-slot cover.

Abstract: The rotating field of a dynamoelectric machine comprises a rotor having electrically conductive windings extending along the axial length of the rotor. The windings are disposed in axially extending slots and the slots include electrical insulation for preventing the transfer of electric current between the windings and the rotor body. A direct cooled generator field is one which is cooled by the atmosphere surrounding the field; e.g., hydrogen or air, and is designed so that the gas coolant is pumped radially through the windings and axially through sub-slots in the rotor body. The present invention is concerned with sub-slot covers which are designed to improve the electrical insulating properties of the cover by increasing the electrical path length between the windings and the rotor body and by obviating the formation of electrical paths due to the possible accumulation of foreign material.