An advanced propulsion motor with enhanced winding cooling system for a solar-powered aircraft

Solar-powered aircraft are being upsized and required to carry more payloads, which poses great challenges for propulsion motors, especially for their cooling considering extreme lightweight. Due to remarkable thermal performance, heat pipes (HPs) become one of the most promising solutions for aircraft propulsion motors. However, this may also lead to extra losses, which requires a more intensive study to maximize HP thermal benefits and minimize motor losses. In this paper, a propulsion motor with an HP-based winding cooling system is developed, and the effects of HP insertion on motor performance are investigated. Firstly, a motor topology is proposed, and five HPs of different sizes are selected from the market as candidates, with their thermal properties experimentally measured. Then, an appropriate HP size is determined based on a comprehensive evaluation of the thermal performance and losses of the motors with candidate HPs. Finally, the above results are verified by motor prototyping and testing. Both simulation and test results indicate a significant improvement in cooling capacity, as well as extended motor performance boundaries.