Design And Optimization Of Asymmetrical Rotor Configuration For PM-assisted Synchronous Reluctance Machine

With the development of the times,the demand for high performance machines in industry,automobile and other fields has increased,so permanent magnet synchronous machines are widely used.However,due to the continuous exploitation of rare earth resources,the world’s rare earth reserves are decreasing,and rare earth resources have become national strategic reserve resources.In order to reduce the dependence of permanent magnet machines on rare earth permanent magnet materials and at the same time to achieve high performance,permanent magnet assisted synchronous reluctance machine(PMA-Syn RM),as a high reluctance machine,has become one of the current research hotspots.In this dissertation,the PMA-Syn RM is designed and optimized in three aspects: torque density,torque ripple and magnet cost.This dissertation introduces the working principle of the permanent magnet assisted synchronous resistance machine.The vector diagrams and a simplified analytic model were established by neglecting core saturation and cross-coupling.According to the design specification of machine,a PMA-Syn RM with symmetrical rotor structure is designed.The initial design scheme of machine is determined from the point of view of main size,the selection of pole slot coordination,rotor magnetic barrier structure and so on.Due to the excessive structure parameters of the rotor and the coupling relationship between the parameters,a parametric model of the rotor was established based on the initial design scheme.The influence of the magnetic barrier position,the opening angle of the magnetic barrier and the bottom width of the magnetic barrier on the torque performance was studied by the finite element method.The influence of the above parameters on the average torque and torque ripple of the machine was analyzed,and multi-objective optimization was carried out for the key structural parameters.On this basis,the optimal design scheme of the machine was obtained,and the performance of the machine was analyzed.By establishing the mathematical model of the asymmetrical machine and using the frozen permeability method to effectively separate the electromagnetic torque,the influence of the magnet-axis-shift effect on torque performance was studied.Based on the optimized symmetric structure,a novel asymmetric PMA-Syn RM using mixed permanent magnet materials was proposed.In this dissertation,two materials of ferrite and Nd Fe B are arranged on both sides of the magnetic barriers,so that the magnetic axis is shifted by the asymmetric arrangement of magnets.By controlling the degree of asymmetry,the angle of magnet-axis-shift is adjusted to improve the utilization of torque components.The novel asymmetric permanent magnet assisted synchronous reluctance machine can reduce the cost of permanent magnets but still achieve similar torque and wider constant power speed range performance.