Modeling, analysis, and optimization of the asymmetric cooling system for a hybrid oil-cooled motor

To address the issues of uneven oil distribution and excessive local temperature rise in oil-cooled Permanent Magnet Synchronous Motors (PMSMs), a novel triple-pipe cooling structure with double-hole nozzles is developed in this article. Then, an asymmetric 3D thermal network model is proposed considering the temperature dependence of oil parameters and air gap friction loss to accurately describe the motor’s temperature distribution. Compared to traditional models, the proposed model demonstrates a 35 % improvement in accuracy. Next, the effects of the cooling structure and medium on the motor’s temperature distribution are analyzed. The results indicate that the winding temperature with the dual-hole and triple-pipe configuration is reduced by 32.96 %, 28.04 %, and 3.97 % compared to the single-hole single-pipe, dual-hole single-pipe, and dual-hole dual-pipe structures, respectively. The winding temperature with the cooling medium of Mobil oil is lower by 0.99 % and 3.29 % compared to ATF oil and Engine oil respectively. Furthermore, to optimize the cooling structure, a two-layer multi-objective optimization method is proposed with the employment of Taguchi’s method and Grey Fuzzy Logic. Finally, the optimized prototype of the motor is fabricated, and the experimental platform is developed. Experimental results indicate that the proposed optimization method can effectively improve the heat dissipation performance of the motor cooling structure. The optimized PMSM temperature decreases by 5.5 % under steady-state condition, and by 10.35 % and 10.92 % for stator and winding temperature under transient condition, respectively.