| Modular multi-element flux-switching permanent-magnet(MMEFSPM)machines alleviate the serious stator saturation in the traditional stator-permanent-magnet flux-switching(SPM-FS)machines,and inherit the principle of flux switching and the flux-concentrating effect,thus,relative higher torque density and greater overload capability can be achieved in MMEFSPM machines,which is therefore expected to be used as in-wheel traction machine of electric vehicles(EVs).Because the structure of it is similar to the common spoke-type permanent-magnet machine,MMEFSPM machine is also called modular-spoke-type permanent-magnet(MSTPM)machine,which will be used in this thesis.Considering the performance and structure of hub machines are heavily dependent on the thermal constraints and there is a strong coupling effect between the thermal field and the electromagnetic field,thus,the multi-physics performance analysis based on the bidirectional coupling between the temperature field and the electromagnetic field is deeply analyzed in this thesis with the MSTPM machine as the research object.Firstly,an improved modeling method of exact subdomain method is proposed for MSTPM machines,and the electromagnetic field of a MSTPM prototype machine is calculated by analytical model.And then,the modelling method of thermal network is analyzed with the coupling effect considered between the electromagnetic field and thermal field.Also,the two-way coupling iteration calculation is realized in this thesis,and a more accurate temperature performance prediction can be obtained compare with that by the traditional one-way coupling method.The innovations and main research contents are as follows:(1)The current research status of electromagnetic field and temperature field of machines are(1)The current research status of electromagnetic field and temperature field of machines are summarized,and the shortcomings of existing research are expounded.In addition,the innovations and necessity of this research are pointed out.(2)The structure and working principle of MSTPM machine are analyzed.Furthermore,the electromagnetic torque characteristics are analyzed and finite element method(FEM)simulation is conducted,which proves the existence of the reluctance torque.(3)An improved modeling method of exact subdomain method is proposed for MSTPM machines with a prototype machine being modeled by the improved method,which solves the problems,such as satisfying the boundary conditions between the air gap and the rotor tooth and decrease the cogging torque error.(4)A thermal network modeling method is proposed for MSTPM machine,and the analytical expressions of convective heat transfer coefficient of the hub and end caps are established.Besides,an analytical method for calculating the transient temperature rise in thermal network is derived,which solves the problems in traditional numerical operations,including sensitivity to step size,convergence uncertainty,computational difficulty.The results of thermal network model are verified by the FEM simulation.(5)A two-way coupling electromagnetic field and thermal field analysis method is proposed for MSTPM machines,which comprehensively analyzes the interaction between the electromagnetic field,the temperature field and material properties of the machine through iterations,and can achieve higher accuracy in both steady-state temperature distribution and short-term transient temperature rise predictions compare with that by the traditional one-way coupling method.FEM is adopted to verify the effectiveness of this method.(6)An experiment platform is built with a 2.1 k W MSTPM prototype.A series of experiments,including steady-state temperature distribution experiments and transient temperature rise experiments,are carried out to verify the above theories,which proves the effectiveness of proposed two-way coupling method. |
PDF Full Text Request