Research On Magnetic Characteristics Of Surface Mount Permanent Magnet Synchronous Motor Based On Accurate Sub-domain Method

With the development of rare-earth permanent magnet materials,permanent magnet synchronous machines have attracted extensive attention from scholars.Compared with conventional machines,permanent magnet synchronous machines have the superiority in reliable operation,high efficiency,flexible shape and size.Therefore,permanent magnet synchronous machines are widely used in aerospace,electric vehicles,industrial production,agricultural production and other fields.However,due to its own structural characteristics,this type of machines still have many problems to be solved in engineering.This thsis focuses on the analytical calculation method of magnetic field,calculation and suppression of cogging torque,calculation and optimization of various losses and other key magnetic problems of surface-mount permanent magnet synchronous machines.The main research work includes the following aspects:An accurate sub-domain model for calculating the magnetic field performance of the machines with permanent magnet chamfering structure is proposed.In order to match the boundary conditions,the chamfered permanent magnet is equivalent to a double-layer sector permanent magnet,and the equivalent magnetic circuit method is used to determine the key dimensions of the permanent magnet after the equivalent.On this basis,the machine is divided into four sub-domains: inner permanent magnet,outer permanent magnet,air gap,and stator slot.Under the boundary conditions,the Poisson equation or Laplace equation satisfied by each sub-domain is solved by the separating variables method,and the analytical solution and harmonic decomposition of the air gap magnetic flux density in improved machine model are obtained.This method realizes combination of magnetic circuit method and magnetic field method.By comparing the calculation results of the analytical method and the finite element method,the advantages of the algorithm are discussed in terms of calculation accuracy and calculation speed.Using the Maxwell tensor method,the cogging torque of the surface-mounted permanent magnet synchronous machine is analyzed,and the value of the air gap flux density component is obtained by the sub-domain method.It was verified by the finite element method.Then,the weakening effects of the chamfer angle,chamfer length,and pole slot parameters of the cogging torque are studied separately,and the parameter optimization scheme that the best cogging torque weakening effect is determined.Finally,the influence of the optimized structure on the electromagnetic performance of the machine is studied.Aiming at the calculation and suppression of various losses of surface-mounted permanent magnet synchronous machines,researches are carried out on winding copper loss,iron core loss,and permanent magnet eddy current loss.First,the mechanism of core loss,winding copper loss,and permanent magnet eddy current loss are analyzed and their expressions are derived.Then,the various losses of different permanent magnet chamfered structure optimization models are solved and analyzed.The finite element calculation results show that the proposed optimized structure has different degrees of weakening effects on the various losses of the prototype.