Thermal Modeling and Analysis of a HPMSM Coupling With Magnetic Bearings

The supercritical CO2 Brayton cycle (S-CO2 BC) has attracted increasing attention because of the advantages of high efficiency, better compatibility, and safety, and to further improve the power density, turbine alternator compressor (TAC) integrated high-speed permanent magnet synchronous machine (HPMSM) sets are usually used in S-CO2 BC power generation devices. In terms of safe operation, it is of great significance to accurately and quickly obtain the temperature in the coupling state of the machine and magnetic bearings. Taking a 40000rpm HPMSM set used in S-CO2 BC power generation devices as an example, a new equivalent thermal model of winding is proposed firstly, and the temperature difference between the equivalent model and the exact model is less than 1.7%. On this basis, the lumped parameter thermal network (LPTN) model of the HPMSM set under the coupling state of the machine and magnetic bearings in totally enclosed environment is established. Finally, the steady and transient temperature results of the HPMSM set are obtained, which are verified by computational fluid dynamics (CFD) method. The range of absolute temperature error between LPTN model and CFD model is 0.2°C~2.2°C in steady state, and the relative temperature error is less than 4.2% in transient state. Furthermore, the computational efficiency of LPTN model is greatly improved compared with CFD model. The research of this paper is of great significance to temperature analysis and prediction under the coupling state of machine and magnetic bearings.