An Enhanced PMSM Cooling Design for Traction of an Electric Vehicle

A novel cooling design is proposed to improve the power density of a radial flux permanent magnets synchronous motor (PMSM) with an internal rotor and hairpin windings. It provides additional overall cooling capability and targets the hot spots that typically limit the motor performance: the stator end windings and the rotor magnets. A water ethylene-glycol mix (WEG) is used as the cooling fluid where the losses are extracted by thermal conduction. The novel end-winding cooling is performed through the motor endplates with a thin layer of thermal encapsulant. The magnet cooling is done using the available coolant in the backplate for the end windings and feeding it to a lance that allows it to enter the rotating hollow shaft. The geometry and the properties of the materials considered are used to build a thermal model. An existing electric vehicle (EV) traction reference PMSM is presented as a baseline, and a cooling proof of concept (PoC) is built for experimental validation of the enhanced cooling. The testing setup is presented, and test results are analyzed. The experimentally validated thermal model is then used to extrapolate the cooling design's application to a full prototype, and the expected benefits are quantified.