Rotor Investigation of High-Speed Permanent Magnet Motor with Roundness Error and CFD-Thermal Distribution Analysis

The rotor overtemperature caused by losses is one of the important issues for the high-speed electrical machine. This paper focuses on the rotor loss analysis and CFD-thermal coupling evaluation for 105 kW, 36,000 r/min HSPMSM. Three types of sleeve materials as carbon-fiber, Titanium alloy, and stainless steel are introduced in this paper, researching the effects of sleeve conductivity, thickness and rotational speed on rotor eddy current loss, balancing rotor mechanical strength. The sleeve made of titanium alloy material with a thickness of 3.5 mm is chosen to effectively suppress the rotor eddy current loss in high-speed motors in the paper. The air friction loss becomes significant based on the PM motor at high rotational speed. The roundness error of the rotor sleeve has the important impact on the air friction loss of the rotor and the rotor temperature of the motor, which leads to the over temperature of the rotor. Therefore, based on the CFD fluid model, the influence of roundness error, cooling parameters, rotational speed and temperature boundary on the air friction loss is studied in detail, and the expression is summarized to provide reference for estimating the air friction loss. According to the rotor structure in this paper, the optimal cooling air inlet velocity is 10 m/s. Finally, the loss separation method is used to obtain the air friction loss measurement results. The accuracy of the finite element calculation results of air friction loss is verified through the experimental data. The temperature rise of the HSPMSM was also measured with 5.5% error. In this paper, the conclusion and analysis method could provide some reference for the research of the rotor structure and the improvement of the efficiency of HSPMMs.