Analysis And Design Of Axial-Flux Permanent-Magnet Machine For In-Wheel Traction

Due to the compact configuration,high efficiency and high torque density,the axial flux permanent magnet(AFPM)machines have attracted wide research attention in the field of electric vehicles.The AFPM machines have a variety of topologies,among which the single-stator single-rotor(SSSR)AFPM machine and the single-stator double-rotor(SSDR)AFPM machine are the research hotspots.The yokeless and segmented armature(YASA)machine is a special configuration of the SSDR-AFPM machine,which has no yoke,significantly reducing the stator weight and iron loss.Hence,the YASA machine is very suitable for in-wheel traction applications due to high power density and efficiency.In this thesis,the YASA machine is optimized and analyzed.A comparative study between SSSR-and SSDR-AFPM machines is carried out,from the aspects of the torque performance,the loss and the speed range.Besides,the lumped parameter thermal network model of YASA machine is established to investigate its thermal characteristics.Finally,the prototyped YASA machine is manufactured and tested to validate the design and analyis.The main research contents are arranged as follows:Firstly,the quasi-3-D computation method is introduced to save the computation burden of the three dimensional(3-D)finite element method(FEM)of AFPM machine,followed by the error analysis.The Taguchi method is applied in the optimization of YASA machine,and the machine configuration parameters are optimized by the sensitivity analysis results.Then,the performance of the optimized design is analyzed in detail,including no-load back electromotive force,cogging torque,axial magnetic pull force and the rated torque.Secondly,a comparative study is conducted between SSSR-and SSDR-AFPM machine.The SSSR-AFPM machine includes two configurations: the single stator single rotor model I(SSIM)and the single stator single rotor model II(SSIIM).The comparison of the torque performance and the loss between SSIM,SSIIM and YASA machine are conducted.The mathematical model of electromagnetic torque of the permanent magnet machine is established considering magnetic saturation,while the overload performance of SSIM,SSIIM and YASA machine are analyzed by the electromagnetic torque equation.Furthermore,the inductance,the torque performance and the speed range of the Taguchi-optimized SSSR-AFPM machine and YASA machine are compared.In addition,the electromagnetic performance of NN PM structure,NS PM structure and YASA machine are compared.Finally,the thermal network model of YASA machine is built.The construction of thermal network model of each component and the corresponding thermal resistance calculation formulae are derived in detail.The calculation of air-gap thermal resistance and convection heat transfer coefficient of casing surface is highlighted.The machine loss is obtained by FEM,and the calculated loss is given to the thermal network model to computate the machine temperature.Both the FEM results and thermal network model are verified by experimental test results.