Loss Calculation, Thermal Analysis, and Measurement of Magnetically Suspended PM Machine

Temperature rise caused by losses is a key issue for a high-speed machine. This paper deals with loss calculation and thermal analysis of a high-speed magnetically suspended PM machine (MSPMM) with an actual power of 33 kW and rotation speed of 55 332 r/min. The temperature distribution based on the finite element method is obtained by accounting for various losses, which consist of air friction losses, copper losses, and iron losses of a radial magnetic bearing, a combined radial/axial magnetic bearing, and high-speed permanent magnet machine (PMM). A back-to-back test setup with two MSPMM is fabricated for verifying the calculation results. The predicted maximum temperature of rotor is located in the center of the cylindrical permanent magnet, and the value is 143 °C. Except for the rotor, the estimated maximum temperature of the stator parts is located in tooth tips of the motor stator core, the value is 92 °C, and the error between the predicted temperature and the measured one is 9.3%. Total measured losses are 1644.4 W, the estimated total losses are 1536.7 W, the error is 6.5%, and the efficiency of the machine under test is 94.6%. The loss calculation and thermal analysis results are verified by the measured ones.

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