Patent ID: 7777375

Claim:
An electric motor comprising: a frame; a generally annular stator having a circumferential outside diameter, mounted within the frame and defining a central bore; a rotor oriented within the stator central bore, having: a shaft, having a diameter, rotatively coupled to the frame; a generally cylindrical profile rotor lamination stack coupled to the shaft, defining a rotor outer circumference having a diameter and a core length, and further defining therein at least one axial vent for passage of cooling air flow; a generally annular end ring defining an annular lip projecting axially toward the lamination stack; an air gap defined between the annular lip and the lamination stack, in communication with the rotor axial vent, for passage of cooling air flow therethrough; and a rotor cooling air pathway at least partially defined by the air gap and the rotor axial vent, having an inlet area and an outlet area; the electric motor having an output rating of greater than approximately 200 horsepower and a nominal operating speed of approximately 3600 revolutions per minute and further: having a ratio of rotor core length to outside stator diameter greater than approximately 0.7; and defining a rotor cooling air pathway having a ratio of rotor cooling air inlet area to rotor cooling air outlet area of greater than 1.05.