Churning loss characteristics of a wet three-phase high-speed reluctance motor

With the increasing requirements of electro-hydrostatic actuators (EHAs) for power, volume, and pressure, there is a growing tendency in the industry to combine the motor and pump to form a so-called 'motor pump' to improve the integration. In this paper, a novel structure for a wet three-phase high-speed reluctance motor pump is proposed, which can further improve integration by removing the dynamic seal on the pump shaft, thereby avoiding the problems of dynamic seal wear and oil leakage and improving heat dissipation under high-speed working conditions. However, after the motor is wetted, the churning loss caused by immersion of the rotor in the oil causes additional fluid resistance torque. Based on fundamental fluid mechanics, an analytical model of the churning torque of a wet motor was established. To verify the accuracy of the analytical model, a simulation model of churning loss was established based on computational fluid dynamics (CFD), and the churning torque and flow field state were analyzed. Finally, an experimental prototype was designed and manufactured, and a test bench for churning loss was built. The oil churning torque was measured at different speeds and temperatures. The results from the analytical, simulation, and experimental models agreed well. The experimental results validated the analytical model and CFD simulation. This research provides a practical method for calculating the churning loss and serves as guidance for future optimization of churning loss reduction.