Magnetothermal Coupling Analysis Of Compound Excitation High Speed Permanent Magnet Synchronous Motor

High Speed Permanent Magnet Synchronous Motor(HSPMSM)stands out in the field of high-speed motor due to its advantages of high efficiency,high power factor and large speed changing range.However,due to its small rotor size,large rotor eddy current loss and difficult heat dissipation,HSPMSM is limited to further development of higher speed and higher power density.Therefore,a new compound excitation rotor structure is proposed in this thesis,which combines the advantages of ferrite permanent magnet with low conductivity and rare earth permanent magnet with high remanence.On the basis of the new rotor structure,the methods of combining theoretical research,Finite Element Analysis(FEA)and prototype test are used to study the modeling and solving of dynamic Magnetic Equivalent Circuit(MEC)model,Lumped-Parameter Thermo-Network(LPTN)model and magnetothermal coupling model of compound excitation HSPMSM,and then the influences of main parameters on motor performances are studied.Firstly,the basic structure and operating principle of compound excitation HSPMSM are introduced,its dynamic MEC model is analyzed and established,in which the calculation methods of reluctance and magnetomotive force are studied.The algebraic equations of dynamic MEC model of compound excitation HSPMSM are established,coupled with the differential equations and then solved.The dynamic MEC model is used to analyze the magnetomotive force,no-load and load performances of the compound excitation HSPMSM,and the analysis results are compared with those of FEA to verify the accuracy of the model proposed in this thesis.Secondly,according to the structural characteristics of the compound excitation HSPMSM,the LPTN models of lapping winding and ring winding are established,the thermal sources and resistances are calculated,and the global steady-state temperature rises are obtained by solving the LPTN.To verify the accuracy of the LPTN,its results are compared with those simulated by Motor CAD software.The temperature rises of the two types of windings are compared and analyzed.Thirdly,the influences of assembly gap,slot size and output power on motor temperature rise are studied.Finally,based on the established dynamic MEC model and LPTN model,considering of the coupling relationship between magnetic field and temperature field,the magnetothermal coupling model of the compound excitation HSPMSM is established.Two HSPMSMs with the same volume but different excitation modes are designed,and their performances are compared and analyzed.The results show that the compound excitation HSPMSM can suppress the rotor eddy current loss and has more advantages in temperature distribution during high-speed operation.The results of this thesis provide the reference for quick performance analysis and design optimization of HSPMSM.