US Patent 7459817 Semi-enclosed AC motor

A partially enclosed induction motor comprises a rotor assembly, a stator assembly, and a metal frame defining a housing having a generally cylindrical shape with bearing housings at each axial end. The interior of the frame is configured to closely embrace a laminated core and follows the contour of the coil end turns of the stator assembly. A canister seal between the stator assembly and the rotor assembly hermetically seals the rotor assembly from the stator assembly. A heat conductive molding material fills gaps in the stator winding and the space between the stator assembly and the frame. A fan driven by the rotor shaft and a shroud direct the air along the canister seal and through the rotor assembly.