Feasibility study of slot thermal management for hairpin windings with embedded ultrathin heat pipe in traction electric machines

This study investigates a novel cooling technique for hairpin windings in high-speed permanent magnet synchronous motors (PMSMs). The increasing demand for high power density in electric propulsion necessitates addressing the challenge of higher current density in compact electric machines. Consequently, thorough research into thermal management systems becomes imperative to effectively address the escalating cooling requirements. Recent trends have witnessed the swift adoption of hairpin windings in traction motors, driven by their advantages such as reduced manufacturing time, precise conductor placement, decreased AC copper loss, and improved copper fill factor in comparison to traditional random windings. The proposed cooling technique uses ultrathin heat pipes to enhance the cooling of solid copper bar windings placed within the stator slots. Heat pipes are highly efficient heat transfer devices that use the evaporation and condensation of a working fluid to transfer heat over long distances. The ultrathin heat pipes used in this study are specially designed to fit within the narrow stator slots of PMSMs. Numerical simulations were conducted to investigate the performance of the proposed cooling method. The simulations showed that the proposed cooling method can significantly improve heat transfer efficiency within the PMSM stator. Hotspot temperatures near the phase current rating were reduced by 10% to 25%. Additionally, heat dissipation from the stator body increased by up to 40%. The improved heat transfer efficiency and heat dissipation achieved with the proposed cooling method can lead to a number of benefits, including increased power density, extended motor life, and reduced operating costs. The proposed cooling method has the potential to be a promising solution for the thermal management of hairpin windings in PMSMs.