Optimized flow rate and efficient shaft water cooling method for EV's PMSM temperature-dependent energy system output power increase

One possible way to enhance the power density of electric vehicle (EV) powertrains is by utilizing temperature-sensitive permanent magnet synchronous motors (PMSMs) managed through liquid cooling. The management of benefits and costs from EV PMSM liquid cooling versus power are carried out for energy system output power (ESOP) increase. This study examines the effects of optimizing flow rate into housing water jackets (HWJ) and implementing compound shaft water (SWJ) cooling as management strategies using numerical multiphysics simulations and experiments. The PMSM with higher temperature at higher speed shows larger profit space brought by enhanced cooling. The optimized HWJ flow rate is a highly-efficient strategy to increase ESOP when overall pumping efficiency e₁ for HWJ is less than 5 %, increasing more than 5.6 %, 2.1 % and 2.4 % ESOP at 1500, 3500, and 7000 rpm continuous working point. ESOP is insensitive to the condition of HWJ flow rate below 6 L/min or e₁ over 30 %. The SWJ cooling is proved to be a low-cost and high-yield energy management strategy roughly independent of SWJ flow rate and EV's cooling system arrangement. ESOP is further increased by up to 3.9 %, 6.2 % and 4.4 % with SWJ cooling at 1500, 3500, and 7000 rpm.