Performance Analysis Of Surface-Mounted Permanent Magnet Synchronous Motor Based On Precise Subregion Method

Permanent magnet motor(PMM)has been widely used in aerospace,industrial and agricultural production and daily life because of its simple structure,small size,high efficiency,various shapes and sizes,and good performance.Permanent magnet motor has many advantages,but because of its physical structure,it will produce cogging torque.Torque ripple is caused by cogging torque,which makes motor produce vibration and noise.When the frequency of torque ripple is consistent with the mechanical resonance frequency of stator or rotor,vibration and noise will be amplified,and the performance of variable speed drive and position control system will also be affected.Therefore,it is very important to study how to reduce or eliminate the cogging torque.The purpose of this paper is to reduce cogging torque and torque ripple in the process of motor design,so as to accurately calculate the electromagnetic torque of the motor.The following are two aspects of the research work done in this paper.:Firstly,Analytical modeling of permanent magnet motor magnetic field considering the influence of cogging.The calculation of magnetic field is an important step in the design of permanent magnet motor,and also a prerequisite for understanding the performance of the motor.In this paper,the surface mounted permanent magnet synchronous motor(PMSM)is taken as the research object,and the precise sub-region method is used to analytically model the magnetic field and electromagnetic torque of the motor.The precise sub-domain model divides the motor into four regions: permanent magnet,air gap,slot and stator slot in two-dimensional plane.In each region,Laplace or Bersson equation is solved by combining boundary conditions,and air gap flux density is obtained.Then,according to Maxwell stress method,slot torque and electromagnetic torque under no-load and load can be solved.Then,taking a 14-pole 12-slot permanent magnet synchronous motor as a prototype model,the simulation analysis is carried out by using Ansoft Maxwell software.The accuracy of the analytical model is verified by comparing the analytical method with the simulation results.At the same time,the simulation results of cogging torque and electromagnetic torque show that the main cause of torque fluctuation is cogging torque.Secondly,Research on the method of reducing cogging torque.The causes of cogging torque are described in detail.The formulas of cogging torque are calculated by energy method and Fourier series method.Based on the analytical formulas,it is found that the main factors affecting cogging torque are air gap magnetic density harmonics and the position relationship between stator teeth and permanent magnet.At the same time,through theoretical deduction,from the angle of changing the pole parameters and armature parameters of permanent magnet,how to optimize the motor parameters to reduce the cogging torque is analyzed.Finally,the finite element analysis of the prototype model is carried out by using Ansoft Maxwell software in four aspects: changing the pole arc coefficient of the motor and the depth of the boot and whether the stator is inclined.The conclusion that reasonable selection of the motor parameters can reduce the cogging torque is verified.Reducing cogging torque can reduce torque ripple and facilitate accurate calculation of electromagnetic torque.