Research On Electromagnetic Performance Of Multi-phase Surface-mounted Permanent Magnet Motor Based On Conformal Transformatio

As a high efficiency and low noise driving device,the large capacity multiphase surfacemounted permanent magnet synchronous motor(PMSM)has been widely used in large ship electric propulsion systems in recent years.The electromagnetic performance of the PMSM is closely related to the air gap magnetic field.Therefore,it is of great significance to calculate the air gap magnetic field of the PMSM quickly and accurately for the analysis of motor operation performance,and the optimization and design of PMSM.In this paper,a nine-phase surface-mounted permanent magnet prototype based on the large capacity multiphase permanent magnet motor is studied by using an improved conformal mapping(ICM)method.The analytical calculation model of the PMSM is established,and it is based on the equivalent surface current method and the conformal mapping method.The permanent magnet is equivalent to an equivalent current model distributed along its surface.The traditional conformal mapping(TCM)method incorporating the Hague equation and the ICM method incorporating complex potential function are used to establish the conformal mapping relationship between the slotted and slotless air gap region,respectively.Therefore,the position of the equivalent current in the slotless air gap region and the expression of the PMSM air gap magnetic density can be obtained.Finally,the convenience of the ICM method is verified by comparing the solving process of the two conformal mapping methods.The operation performance under different working conditions is analyzed based on the air gap magnetic fields of the PMSM.Firstly,two conformal mapping methods are used to calculate the no-load,armature reaction and load air gap magnetic field of the PMSM,and the calculation results of the ICM method and the TCM method are verified by the finite element simulation.And the accuracy,rapidity and universality of the ICM method are further proved.Secondly,the no-load back EMF,cogging torque,load back EMF and load torque of the PMSM are analytically calculated based on the calculation results of the air gap magnetic field.The correctness and feasibility of the proposed method in this paper are further verified by carrying out no-load and load experiments on the experimental prototype respectively.The optimization is carried out to improve the electromagnetic performance of the PMSM,such as torque ripple and air gap flux density.Firstly,according to the optimization objectives and variables,the orthogonal test table is established by the Taguchi method,which means that different motor parameter combination schemes are determined.Secondly,the electromagnetic properties corresponding to different optimization schemes are calculated by the improved conformal mapping method,and the calculated results are analyzed by mean value analysis and variance analysis.Finally,the design scheme that can meet the optimization objectives to the greatest extent is determined based on the analysis results.The research in this paper can provide theoretical guidance for the calculation of air gap magnetic field,electromagnetic performance analysis and motor optimization design of multiphase surface-mounted PMSM with various complex air gap structures.