HEAT TRANSFER ENHANCEMENT OF VENTILATION CHIMNEYS FOR DYNAMOELECTRIC MACHINE ROTORS

A cooling gas ventilation chimney is provided for enhancing the heat transfer of an end region of a dynamoelectric machine. The dynamoelectric machine includes a rotor having a plurality of radial slots. A plurality of coils are seated in the radial slots, and the coils form a plurality of radially stacked turns. The ventilation chimney includes one or more chimney slots defined in at least a portion of the radially stacked turns. The chimney slots extend in a substantially radial direction to the rotor, and some of the chimney slots have an axial or circumferential length different from other chimney slots.