| Interior permanent magnet synchronous machine(IPMSM)has been widely used in electric vehicles and other fields due to its high efficiency and high torque density.However,in order to make full use of the reluctance torque,IPMSM usually has a high current density and the rotor is easily saturated,which leads to a higher torque ripple and loss,thereby causing adverse effects such as vibration,noise,heating and efficiency reduction during the operation of the machine.Therefore,in the process of designing and optimizing IPMSM,it is very important to calculate the torque and loss accurately.In order to suppress the torque ripple of IPMSM,a multi-phase design is adopted in this paper,and a novel five-phase IPMSM with shifted asymmetrical rotor pole is formed by introducing the asymmetric structure and the magnet shifting structure into IPMSM.By optimizing the pole-arc angle and the magnet shifting angle,the torque performance of the machine is effectively improved.On this basis,considering the influence of stator slotting,magnetic saturation effect,asymmetric structure and magnets shifting,the analytical method of permanent magnet torque and reluctance torque for the IPMSM is proposed,and the mechanism of its torque ripple generation and suppression is revealed.In addition,three analytical methods of iron loss based on stator flux density are proposed,which can effectively calculate iron loss and efficiency.The research content of this paper involves the design and optimization of the IPMSM,the analytical calculation of the parameters related to torque and loss,as well as the manufacture and experimental verification of the prototype.It provides theoretical basis and technical reference for the optimal design and analytical calculation of this type of machine.The main research results of this paper can be summarized as follows: 1.A novel five-phase IPMSM with shifted asymmetrical rotor pole is proposed to improve the torque performance.Firstly,a five-phase symmetrical V-type IPMSM is designed by choosing the appropriate phase number and pole-slot ratio according to the requirements.On this basis,the torque ripple of IPMSM is reduced by optimizing the pole-arc angle and magnet shifting angle.At the same time,the torque performance is analyzed to verify the effectiveness of the design method.2.The analytical method of permanent magnet torque for the studied IPMSM is proposed.The analytical expression of stator magnetomotive force(MMF)is deduced by using the winding function theory;the analytical expressions of air-gap flux density and rotor MMF generated by permanent magnet are deduced by using the equivalent magnetic circuit model;the analytical expression of the torque is derived by using the Lorentz force law.At the same time,in order to improve the precision of torque calculation,the influence of asymmetric structure,magnet shifting and stator slotting effect are fully considered.In addition,the validity of the analytical method is verified by the finite element method(FEM),and the generation and suppression mechanism of the torque ripple are analyzed.3.The analytical method of reluctance torque for the studied IPMSM is proposed.The analytical expressions of rotor MMF generated by stator MMF are deduced in detail by using the equivalent magnetic circuit model;the influence of the stator magnetic saturation effect on the rotor MMF is considered by using the iteration procedure;and the reluctance torque and electromagnetic torque are calculated by using the analytical expression of torque.In addition,the validity of the analytical method is verified by the FEM.4.Three loss analytical methods for the studied IPMSM are proposed.The load air-gap flux density,the stator tooth flux density,the stator yoke flux density and iron loss,which take into account the magnetic saturation effect of the stator,are derived step by step,and verified by the FEM.5.An experimental prototype of five-phase 40-slot 8-pole IPMSM with shifted asymmetrical rotor pole is fabricated.The experimental platform is built and tested,and the performance parameters such as no-load back-EMF,electromagnetic torque and efficiency are obtained,which verifies the validity of the analytical method. |
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