Simulation Analysis And Optimization Of Electromagnetic Noise Of Permanent Magnet Synchronous Motor In Electric Vehicle

The vibration and noise of permanent magnet synchronous motor is one of the important indicators of motor performance evaluation.For automotive drive motors,motor electromagnetic noise is an important part of motor noise,directly affecting the comfort and safety of the driver.The electromagnetic noise of a permanent magnet motor is caused by the electromagnetic force acting between the stator and rotor acting on the surface of the stator to generate vibration.The electromagnetic force between the stator and the rotor includes the radial electromagnetic force and the tangential electromagnetic force,and the tangential electromagnetic force generates the torque.The radial electromagnetic force is the main cause of the electromagnetic vibration noise,and is also the main research object of this paper.Permanent magnet synchronous motor electromagnetic noise is a multi-physics coupling problem involving motor theory,motor electromagnetic field,motor structure modal analysis,motor structure forced vibration and acoustics.Due to the complex structure of permanent magnet motor,many factors are considered in the calculation process of electromagnetic noise electromagnetic noise.In this paper,the electromagnetic field,motor structure and sound field finite element model are established respectively to calculate the electromagnetic vibration and noise response of the motor.Comparing the experimental test results,the motor electromagnetic noise simulation results are more accurate,providing a basis for analyzing the electromagnetic radiation noise of the motor.In order to comprehensively analyze the electromagnetic vibration and noise of the motor,this paper uses the Maxwell tensor method to derive the magnetic field and electromagnetic force expression of the permanent magnet synchronous motor.Determine the relationship between the electromagnetic force spatial distribution characteristics,the electromagnetic force excitation frequency,the motor pole pairs,and the current excitation frequency under motor load conditions.According to the actual size of the motor,a two-dimensional finite element model of the motor magnetic field is established.The model considers the influence of nonlinear factors such as magnetic field saturation and permanent magnet material on the magnetic field,and calculates the magnetic flux density and electromagnetic force of the motor air gap.The simulation results show that the electromagnetic force distribution characteristics are in good agreement with the theoretical derivation results,and the reliability of the motor magnetic field finite element model.The research found that:(1)Frequency of the electromagnetic force is an integral multiple of the number of poles of the motor,the magnitude of the electromagnetic force is large,which is also a reference method for the motor to avoid resonance.(2)The electromagnetic force of the motor mainly acts on the inner surface of the stator core.The inner surface of the permanent magnet motor stator core is excited by electromagnetic force to generate forced vibration.Therefore,the inherent mode shape,modal frequency and damping ratio of the motor structure are also one of the key steps to study the vibration and noise of the motor.In this paper,the single mode method is used to briefly describe the main mode shape of the motor structure and the natural frequency.However,the mathematical model has certain limitations and cannot accurately calculate the motor modal results.Therefore,the paper uses the method of reverse scanning to establish the geometric model of the motor,and establishes the three-dimensional finite element model of the motor constraint according to the geometric model of the motor.The modal shape and corresponding frequency of the motor 0-6000Hz are calculated and analyzed.The electromagnetic force is coupled with the motor modal result,and the modal superposition method is used to calculate the electromagnetic vibration response of the motor.The error compared with the experimental test results is small.It is further determined that the two-dimensional finite element model of the motor electromagnetic field and the finite element model of the motor structure are accurate and meet the requirements of engineering applications.The finite element method is used to calculate the electromagnetic vibration noise of the motor,and the influence of the electromagnetic vibration noise distribution is also studied.To calculate the motor noise by using the finite element method,it is necessary to establish an acoustic grid.The vibration response of the motor surface is used as the excitation source to calculate the radiation pressure of the corresponding test point outside the motor.The calculation results of the sound pressure component of the electromagnetic noise of the motor agree well with the test results of the semi-compliance chamber.Compared with the experimental test,it is correct that the motor electromagnetic noise simulation process and the finite element model are correct.Based on the original motor model,this paper proposes an optimization scheme for the opening of the auxiliary rotor on the rotor surface of the motor.The finite element method is used to compare the radial electromagnetic force component of the auxiliary rotor and the electromagnetic vibration noise of the motor.It is found that the motor rotor can be effectively reduced to reduce the electromagnetic radiation noise of the motor.Studies have shown that the rotor surface is provided with the feasibility of an auxiliary tank optimization scheme.In this paper,the analytical model and finite element model of the electromagnetic field,motor structure and sound field of the motor are established.The multi-physical coupling method is used to accurately calculate the low-frequency vibration response and radiation noise in the motor.Explain the mechanism of electromagnetic radiation noise,and analyze the relationship between magnetic flux density,electromagnetic force and vibration noise of the air gap magnetic field of the motor.Finally,a method for modifying the rotor structure of the motor is proposed.The method can effectively reduce the electromagnetic radiation noise of the motor,and provide ideas for the motor manufacturer to analyze the vibration and optimization of the motor.