Research On Electromagnetic Vibration And Noise Analysis Of Interior Permanent Magnet Synchronous Motors For New Energy Vehicles

Interior permanent magnet synchronous motors（IPMSM）are widely used in electric vehicles,vessels,intelligent home appliances and other fields because of their its high efficiency,high torque density and high power factor.In these applications,due to the pursuit of comfort and practical needs of customers,whether the motor can be quiet and stable operation has become an important selection index,so in recent years the vibration and noise problems of permanent magnet synchronous motor has attracted widespread attention.This article focuses on the electromagnetic vibration and noise problem of a new energy vehicle with IPMSM.Firstly,the source of electromagnetic noise of this motor is analyzed,and the mechanism of electromagnetic force wave generation is analyzed from the air gap magnetic field in the case of sinusoidal wave and inverter power supply.The force wave order and frequency,which have a great influence on the electromagnetic vibration and noise,are analyzed,and the air gap magnetic density and electromagnetic force wave density under sine wave and inverter power supply are obtained by finite element simulation analysis.The analysis results show that when the motor is running under load,the electromagnetic force wave amplitude will increase and new force wave order and frequency will be added due to the armature response of the winding current,and the force wave order and frequency are characterized as（6kp+2p,2f₀）and（6kp+2p±i Z,2f₀）.The analysis results when the motor is driven by frequency inverter shows that the high-order time harmonic currents will generate new component in the radial electromagnetic force spectrum with a frequency characteristic of f_c±3f₀.Then,the factors affecting the natural mode of the motor stator system of this motor are investigated.Based on the analytical method of double-loop theory,the natural mode and frequency of the stator system are calculated,and the finite element models of the stator system and the front and rear end caps are established.The natural modes of the stator system and the front and rear covers are simulated and analyzed,and the influence of the housing and front and rear end caps on the stator system natural mode and frequency is analyzed.The results show that after adding the front and rear end caps,the short shaft length of the end caps and the difficulty of radial vibration will restrict the radial vibration of the stator and increase the frequency of the main modes of the stator system.In order to solve the problem that 48-frequency electromagnetic noise generated by the first-order tooth harmonics of this motor is too large,the method of rotor segmented skew-poles and rotor opening auxiliary slots is used to weaken the radial electromagnetic force wave caused by the first-order tooth harmonics,Thus,the electromagnetic vibration and noise of this motor are weakened.A model for calculating the wave density of the radial electromagnetic force of the segmented skew-poles of the rotor is established.The simulation results show that the 0th-order electromagnetic force caused by the low-order tooth harmonics will reach the resonance condition and excite a large amplitude noise when it is close to the 0th-order intrinsic frequency of the motor stator,and the 48-frequency electromagnetic noise generated by the 0th order 12f₁electromagnetic force caused by the tooth harmonics in the high speed region can be effectively weakened by using the rotor segmented skew-poles and the rotor open auxiliary slot.Finally,the prototype was fabricated and tested for electromagnetic performance and noise experiments.The experimental results show that the optimized rotor structure effectively weakens the 48-frequency electromagnetic noise generated by the 0th order 12f₁electromagnetic force caused by the first-order tooth harmonics.