Patent ID: 7186156

Claim:
A propulsion unit for propelling a waterborne vessel, comprising: a) an electric motor for providing propulsion, the motor including a rotor having a cylindrical body mounted upon a shaft having an axis of rotation, the cylindrical body including rotor windings, a first cooling passage being provided between the cylindrical body and the shaft, and a second cooling passage being provided through the rotor windings; b) a housing for containing the motor and bounding an interior through which a cooling gas is passed longitudinally of the rotor along the first cooling passage in a first direction and along the second cooling passage in a second direction different from, and opposite to, the first direction, the interior being maintained at an increased pressure of above roughly 2 bar to increase a cooling effect of the cooling gas; and c) a heat exchange region including fins provided on an internal surface of the housing between the first cooling passage and the second cooling passage.