SUMMARY

Permanent magnet synchronous motors (PMSM) are commonly used in electric vehicle (EV) powertrains because of their high power and torque densities. In a high-power-density electric motor, major heat loss occurs in the windings in the form of resistive heating. In a typical liquid-jacket cooled motor, high thermal resistance between the winding and the cooling medium limits heat extraction. Therefore, by moving the coolant closer to the winding, thermal resistance between the winding and coolant can be significantly reduced, and hence, the winding temperature can be maintained below the thermal limit. This study numerically compares the electro-thermal performance of three embedded cooling techniques, namely direct winding heat exchanger (DWHX), embedded circular, and rectangular cooling channels within stator core, with conventional jacket cooling (JC). The results confirm that the DWHX approach provides the best performance compared to the other cooling techniques. However, DWHX suffers from high winding-liner contact resistance. To enhance the heat extraction by eliminating the winding-liner contact resistance, this research examines a novel concept of capillary flow-assisted evaporative cooling (EC) confined in-between slot liner and active winding. Electro-thermal performance of the EC has been assessed and compared with JC using a combination of modeling and motorette testing. By leveraging the enhanced electro-thermal performance of EC, this dissertation presents an optimized design of a high-speed heavy rare-earth-free PMSM to meet the U.S. Department of Energy’s 2025 power density target of 50 kW/L for EV motors. The effectiveness of EC has also been assessed for different motor topologies and slot sizes. Moreover, to overcome the high leakage risk of EC, a novel 3D-printed hollow liner cooling concept has been proposed, and the thermal performance of the single-phase hollow liner cooling concept has been experimentally evaluated using an in-house motorette test bench. Meeting link- https://rb.gy/uity2y