Research on Multiphyics bidirectional coupling for small-diameter high-speed submersible permanent magnet synchronous motor

The small-diameter high-speed submersible permanent magnet synchronous motor (SHS-PMSM) is essential equipment for rodless oil and gas extraction in slimhole wells and high-water content oil wells. The SHS-PMSM typically operates for extended periods of time underground in high temperatures. Because of its compact size, the heat is difficult to dissipate, which increases the risk of motor overheating and damage. In order to accurately predict temperature, the method of magnetic-heat-flow multiphysics bidirectional coupling is studied in this paper. A SHS-PMSM with an outer diameter of ø89mm is taken as the object, and its copper loss, friction loss and convective heat transfer coefficient are studied by analytical derivation. The relationship between them and temperature are expressed by functions which can be compiled into User-Defined Functions (UDFs) as variable during the calculation process of finite volume method. Both coupling calculations and experiments are conducted. The temperature calculated by magnetic-heat-flow bidirectional connection is higher than that produced by the conventional method and more in line with experimental results after the results of both simulations and experiments are carried out and compared. The accuracy of the magnetic-heat-flow bidirectional coupling method is verified and the design basis of temperature for SHS-PMSM can be provided.