Performance Analysis And Influencing Factors Study Of The Flux-Torque Regulation Hybrid Excitation Machine With Axial-Radial Magnetic Circuit

Compared with the conventional permanent magnet(PM)synchronous machines,the hybrid excitation machines(HEMS)have the advantages of easy magnetic field regulation,wide speed range and high efficiency.Therefore,the HEMS have a wide range of application in industrial drives,new energy generation and other fields.In this paper,a novel flux-torque regulation hybrid excitation machine with axial-radial magnetic circuit(FTRHEM)is proposed,which innovatively realizes the excitation winding using axial excitation structure not only can regulate the main air gap magnetic field of the machine,but also can generate an additional torque to increase the output torque of the machine,especially the additional torque can compensate for the reduction of the output torque in the flux-weakening condition.In this paper,the following research work is carried out on the structural characteristics,three-dimensional magnetic field analysis,magnetic circuit calculation,machine performance,and influence of influencing factors of the FTRHEM.The topology of the FTRHEM is discussed,and its magnetic field regulation mechanism and additional torque generation mechanism are revealed by studying the structural characteristics and flux paths.The three-dimension(3D)finite element analysis(FEA)is used for electromagnetic calculation and analysis to investigate the variation of its no-load back electro-motive force(EMF)and additional torque under different excitation states,and then clarify its flux regulation capability and improving output torque.Combining the principle of excitation current regulation of the magnetic field,the equivalent magnetic network(EMN)models of the machine in different modes are established,and the main air-gap flux expressions are derived to reveal the constraint relationship between the magnetic field of the machine and each structural parameter.Combined with the calculation of the parameters of the EMN models,the magnetic chain and no-load back EMF are obtained,and the correctness of the established equivalent magnetic network model is verified by comparing with the results calculated by the FEA.On this basis,the effects of key factors on the magnetic field,the flux regulation capability and the additional torque of the machine are studied to provide a theoretical basis for the subsequent optimization of the machine.The key factors include the dimension of the ferromagnetic bridge,the saturation point of the ferromagnetic bridge material,the length of the radial air gap,and the length of the axial air gap.The excitation winding is applied alternating current,which can lead to high eddy current losses in the machine.To solve this problem,a solution is proposed by replacing the Steel-1010 material used for the ferromagnetic bridge and rotor with a soft magnetic composite(SMC)material.A comparative study of machine eddy current losses using the two materials is conducted to verify that the application of SMC can significantly reduce machine eddy current losses.The effects of the two materials on the machine flux regulation capability and the additional torque are compared to comprehensively evaluate the feasibility of using SMC for machine.Two FTRHEM prototypes are made,and an experimental test platform is built.The noload back EMF,flux regulation capability and additional torque of the prototype are tested,and the results obtained are compared with the FEA results to verify the feasibility of the machine principle.