Experimental Investigation of Heat Pipe Inclination Angle Effect on Temperature Nonuniformity in Electrical Machines

Heat pipes (HPs) are gaining increasing popularity in the propulsion motors of transportation electrification due to their remarkable thermal properties. However, the inclination angle affects the HP thermal performance and, thus, results in temperature nonuniformity, which may generate unbalanced thermal stress on the motor. Such an issue has received less attention to date and requires corresponding solutions. This article performs an experimental investigation on motor temperature nonuniformity with HPs and further proposes an improved structure to address this problem. A specimen based on a stator-winding assembly with HPs is prepared and a dedicated experimental platform is established. Then, the temperature distribution across the specimen is studied, followed by an evaluation of the effects of current density and wind velocity. To compensate for the degradation of HP thermal performance, an improved structure with enlarged fins is proposed, and the equilibrium point is determined by fitting and comparing the obtained temperature data. Finally, the proposed structure is verified by the comparison between the original and improved specimens. The experimental results show that the non-uniform temperature distribution is significantly improved, with the temperature range and standard deviation reduced by 42% and 44.3%, respectively.