Electromagnetic-Thermal Analysis And Optimization Design Research Of Permanent Magnet Eddy Current Couplers

As an emerging flexible energy-saving transmission device,the permanent magnet eddy current coupler can transmit torque without rigid contact and mechanical connection,has changed the traditional mechanical transmission operation mode.Its related theories and technologies have become the research hotspots of academic circles at home and abroad.The highly complex research of the permanent magnet eddy current coupler is to solve the electromagnetic field coupling problem of the moving conductor eddy current induced magnetic field and the permanent magnet rotating magnetic field,and the coupling problem of electromagnetic-thermal multiphysics.In the dissertation,the axial flux permanent magnet eddy current coupler is taken as the research object.Based on the electromagnetic field modeling analysis considering the dynamic eddy current problem of the moving conductor,the electromagnetic-thermal bidirectional coupling analysis method is studied to solve the problem of the permanent magnet eddy current coupler's multiphysics coupling analysis.In order to improve the sinusoidality of the air gap magnetic density,increase the power density and suppress the torque ripple,a design method based on the harmonic injection into magnet optimization theory and an optimized magnetic pole arrangement based on combined magnets are proposed respectively.The electromagnetic-thermal coupling analytical models are established and the multiphysics optimization designs are studied.These researches have important scientific significance and academic value,and will supply a new theory and technical route for the permanent magnet eddy current flexible transmission.The specific research contents are summarized as follows:(1)For the problem that the induced magnetic field generated by the dynamic eddy current of the moving conductor is coupled with the rotating magnetic field of the permanent magnet,a two-dimensional electromagnetic analytical model considering eddy current effect is established to analyze the magnetic field distribution and torque characteristics.The analytical model is validated by three-dimensional finite element analysis and 15 kW prototype experiment.On this basis,a quasi-three-dimensional electromagnetic field model based on sub-loop calculation method is established to calculate the magnetic field distribution,the eddy current loss and torque characteristics accurately.It solves the problem that the existing analytical model cannot calculate the eddy current loss distribution,and the highest temperature of the permanent magnet eddy current coupler can be predicted accurately.(2)To overcome the shortcoming that the existing electromagnetic field analytical model is only suitable for the small slip condition,a novel electromagnetic-thermal bidirectional coupling analytical model is presented to calculate the temperature distribution and torque characteristics.The analytical model considers the change of material electromagnetic and thermal characteristics under temperature,and is valid for the whole working area.The analytical model is verified by three-dimensional finite element analysis and 15kW prototype experiment.It solves the problem of the multiphysics coupling analysis of the permanent magnet eddy current coupler,which eliminates the risk of permanent magnets irreversible demagnetization caused by eddy current losses.At the same time,it also solves the problem that the calculation time of three-dimensional finite element method is too long,and is more adaptative for the structural research and optimization.(3)In order to improve the sinusoid of the air gap magnetic density and increase the power density,a design method of the permanent magnet eddy current coupler based on harmonic injection into magnet optimization theory is proposed,which effectively reduces harmonic loss,improves the output torque greatly and achieves the maximum output torque increased by 11.22%.An analytical model that accurately reflects the three-dimensional distribution of the magnetic field and eddy current is established,to analyze the eddy current loss,temperature distribution,torque characteristics and the influence of temperature rise caused by loads increase on the torque accurately.The analytical model verifies its accuracy and superiority by three-dimensional finite element analysis,and provides a fast and accurate calculation method for electromagnetic-thermal coupling analysis.On this basis,a new type of the conductor plate structure is proposed,which is optimized based on the electromagnetic-thermal coupling analytical model.The optimized structure has better torque characteristics and overload capability.(4)In order to inhibit the torque ripple,an optimized magnetic pole arrangement based on combined magnets is proposed,which effectively improves the utilization of permanent magnet materials,and increases the rated torque.The electromagnetic-thermal coupling analysis is carried out.The torque ripple is restrained by 51.03%and the rated torque is enhanced by 3.51%.On this basis,a variety of combined magnetic pole arrangements are proposed,and the sensitivity analysis of structural parameters is carried out.The structural parameters are optimized based on the electromagnetic-thermal coupling analytical model.The optimal structure has better torque characteristics and higher material utilization.Considering the influence of temperature distribution,a multiphysical field optimization design method is put forward.