A Comprehensive Review and Experimental Investigation on Heat Pipes Application in Electrical Machines

The rapid development of transportation electrification brings unprecedented opportunities and challenges as well to the technological improvement of high-power-density motors. As the major restriction of motor performance, thermal issues attract more attention recently and the heat pipe (HP), due to its high thermal conductivity and lightweight characteristics, is identified as a promising solution. Though HPs have been attempted in cooling systems of electrical machines, their thermal benefits still need to be fully understood. This article provides a comprehensive review and performs a series of experimental investigations to fill the technology gaps for the HP application in electrical machines. First, the HP technology is briefly introduced, followed by a detailed review on its applications in different locations of electrical machines with corresponding thermal improvements reported. Then, experimental tests are conducted to investigate the correlation between the HPs' parameters and their cooling effectiveness, including cross-sectional shape, bending angle, fins arrangement, and inclination angle. The obtained results and conclusions could provide a guideline for the promotion of HPs in the next-generation electrical machines for future transportation.