Research on Temperature Rise Characteristics and Cooling System Optimization of Ultra‐Low Temperature High‐Speed Permanent Magnet Motors for <scp>LNG</scp> Pumps

Addressing the issues of temperature rise and uneven temperature distribution in ultra‐low temperature high‐speed permanent magnet motors for liquefied natural gas (LNG) pumps, which are caused by long heat dissipation paths and high air gap friction losses during operation, this paper proposes a semi‐enclosed axial flow cooling structure. Taking a 30 kW, 12 000 r/min LNG pump ultra‐low temperature high‐speed permanent magnet motor as an example, the losses in various parts of the motor are calculated by combining finite element and analytical methods. The relationship between air gap losses and fluid characteristics is analyzed, and the accuracy of the model is verified through low‐temperature experiments on a prototype. The fluid‐thermal coupling of the traditional and improved structures of the motor is calculated using the Computational Fluid Dynamics (CFD) method, and their temperature distributions are analyzed. Studied the influence of the number, radius, and inlet flow rate of the improved structure tooth yoke slot on the maximum temperature of the motor. The results show that the improved model can effectively reduce temperature rise and improve the uniformity of temperature distribution, providing a theoretical reference for the design of cooling structures for such motors. © 2026 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.