Analysis On Electromagnetic Vibration Source And Reduction Method Of Interior Permanent Magnet Motor

Interior permanent magnet synchronous motor(IPMSM)is widely used in the field of electric vehicles because of its high torque,high power density and wide speed range.However,this kind of motor is accompanied by the problems of complex structure and high harmonic content of electromagnetic force,which is easy to produce large electromagnetic vibration.Therefore,it is of great significance to carry out electromagnetic vibration analysis and vibration reduction optimization design to improve the comprehensive performance of the motor.This thesis focuses on the electromagnetic vibration of the IPMSM,analyzes the mechanism of the electromagnetic vibration,quickly and accurately finds the electromagnetic vibration source in a wide speed range,and optimizes the design of the IPMSM with low electromagnetic vibration according to the electromagnetic vibration source.The nonuniform distribution of air gap and its influence on electromagnetic vibration of motor are also studied.The main work of this thesis is as follows:The harmonic components of electromagnetic force of motor are analyzed analytically.The relationship between harmonic components of radial and tangential electromagnetic force and the modulation effect of stator teeth on this electromagnetic force with high spatial order are studied.The research shows that besides the low spatial order radial electromagnetic force harmonic components,some low spatial order tangential,high spatial order radial and high spatial order tangential electromagnetic force harmonic components also have great influence on the electromagnetic vibration of the motor.Taking a 48-slot 8-pole integer slot IPMSM as a prototype,the electromagnetic vibration response of the prototype in a wide speed range is calculated by multi-physical field finite element simulation.Combined with theoretical analysis,it is pointed out that the main electromagnetic vibration source of the prototype is the0th-order and 48th-order 12 f radial and tangential electromagnetic force harmonic components produced by the interaction of the fundamental wave of air gap magnetic density and the first-order tooth harmonic.Aiming at the electromagnetic vibration problem of motor,the amplitude of one of the three elements of electromagnetic force is taken as the breakthrough point,an improved motor structure is proposed by adding flux barriers on the rotor of the prototype and opening a semi-circular slot on the outer surface of the rotor to suppress electromagnetic vibration.Gaussian Process Regression Model(GPR)-Particle Swarm Optimization(PSO)algorithm is used to optimize the structural parameters of the improved rotor,and finally the improved rotor structure which can restrain the electromagnetic vibration of the motor to the greatest extent is determined.The electromagnetic force acting on the stator teeth and the electromagnetic vibration response in a wide speed range of the motor before and after the improvement are compared by finite element simulation.The results show that the improved motor can effectively reduce the electromagnetic vibration of the motor under the premise of ensuring the electromagnetic performance.The strength of the improved motor is checked to ensure the rationality of the motor improvement.From the angle of frequency of one of the three elements of electromagnetic force,the electromagnetic vibration of motor is analyzed.the influence of rotor-step skewing on motor electromagnetic vibration is analyzed by finite element simulation and analytical modeling of electromagnetic force,and the reason of poor suppression effect of rotor-step skewing considering elastic-plastic stator material on electromagnetic vibration of motor is explained.It is pointed out that the rotor-step Zigzag skewing can effectively overcome the limitation of straight inclined pole in electromagnetic vibration suppression of motor.According to the electromagnetic force expression of the rotor-step Zigzag skewing derived from the theoretical formula,the electromagnetic vibration response of the motor is calculated by using the finite element software combined with multiple physical fields.The influence of skewing angle andskewing step number on the electromagnetic vibration of the motor is studied,and the selection rules of rotor-step Zigzag skewing angle and segment number are summarized.According to the eccentricity and mechanical stress deformation of the rotor when motor runs,the air-gap variation law of the motor under the condition of rotor dynamic and static eccentricity and mechanical stress deformation is studied.The air-gap permeability function of the motor is modified,and the expressions of air-gap flux density and electromagnetic force of the motor are derived analytically.According to the expressions,the change of harmonic components of electromagnetic force is analyzed.Through two-dimensional Fourier decomposition of electromagnetic force density,the influence of different air gap changes on the amplitude of harmonic components of electromagnetic force is revealed.A multi-physical field joint simulation model of electromagnetic vibration of motor with non-uniform air gap distribution is established.According to the results of electromagnetic vibration response of motor,the influence of rotor eccentricity and uneven air gap distribution caused by mechanical stress deformation on electromagnetic vibration of motor and its variation law are studied.