Thermal Management Integrated With Flat Heat Pipes for In-Slot Stator Windings of Electric Motors

Increasing electromagnetic loads can improve the torque density and power density of electric motors; however, these enhancements are limited by the resultant thermal problems. This article proposes a cooling concept, where flat heat pipes (FHPs) are inserted into the center of the stator slots to directly remove copper loss without consuming power. Detailed thermal models of the FHPs and an electric motor are established using a lumped-parameter thermal network. The thickness of the vapor chamber is found to be the most critical parameter that simultaneously affects the thermal and electromagnetic performance. A case study is carried out on an existing 6-kW drive motor for a ducted fan, and the simulation results are validated through motorette experiments. Research results have shown that a 70 °C hot-spot temperature reduction can be achieved, and more than 80% of the copper loss can be removed by the FHPs. Moreover, the shaft power that the thermally modified motor can provide is expected to be 2.4 times that of the reference motor, and a continuous power density of 4.8 kW/kg can be achieved using air as a cooling agent.