Lightweight thermal management of permanent magnet synchronous machines for extreme power density operation

Taking the drive motor of a hydrogen-oxygen electric pump as a representative example of short-duration ultra-high power density machines, this study investigates lightweight thermal management techniques under extreme power density operating conditions. An evaluation method for the limiting output power is first proposed to determine the theoretical maximum output power of the motor under given constraints. However, the copper loss associated with this limiting operating point exceeds the allowable level of the machine. To address this issue, a novel cooling configuration is introduced, in which cryogenic channels are embedded in the stator slots and supplied with a low-temperature coolant. The proposed structure operates in two modes: immersion cooling and flow cooling. In the former, the vaporization latent heat of a quiescent coolant is utilized to remove heat, while in the latter, forced coolant flow enhances convective heat transfer. To clarify the underlying mechanisms, an energized solenoid is initially adopted as a simplified test object to investigate and compare the heat transfer performance of the two cooling modes, and immersion cooling is further validated experimentally. Subsequently, an 80 kW prototype motor is used as a test platform to conduct both cryogenic flow and immersion cooling experiments, thereby demonstrating the feasibility and effectiveness of the proposed lightweight thermal management approach.