Research On Vibration And Noise Characteristics Of Permanent Magnet Synchronous Motors For Electric Vehicles

Permanent magnet synchronous motors are widely used in electric vehicles and other fields due to the advantages of simple structure,small room,light weight,high efficiency and excellent speed regularity ability.However,the life of the motor and the driving comfort of electric vehicles will be affected by the vibration and noise of the permanent magnet synchronous motor during operation.Therefore,it is of great significance to predict and reduce the vibration and noise of the permanent magnet synchronous motor in the design stage.An analytical calculation model for the no-load air gap magnetic field of the V-shaped interior permanent magnet synchronous motor is proposed in the paper.Based on the twodimensional precise subdomain method,the equivalent analytical magnet motor model is used to replace the initial V-shaped magnet motor model for analytical calculations.The finite element method is used to verify the analytical calculation results and prove the effectiveness of the method.The electromagnetic force density of the motor is calculated according to the Maxwell tensor method.The Fourier decomposition is performed to obtain the amplitude of each order of the radial and tangential electromagnetic force.Through the parametric analysis of the different structures of the motor,it is concluded that the structural parameters of the main magnetic isolation bridge,the air gap length,the auxiliary magnetic isolation bridge and the width of the stator slot opening on the motor performance and electromagnetic vibration are based on the amplitude of the radial electromagnetic force variety.The motor is optimized with a segmented arc eccentric structure on the outer surface of the rotor.The optimal uneven air gap rotor structure is obtained,which reduces the radial electromagnetic force and the cogging torque of the motor under the premise of ensuring the rated torque.The modal analysis of the stator system of the motor is carried out in an unconstrained state.The influence of windings,isolation layer,casing and front and rear end covers on the natural frequencies of each order of the motor is obtained.Since the rotor structure of the motor is changed after optimization,it is necessary to analyze whether the optimized rotor structure meets the strength requirements.The relationship between the stress and deformation of the rotor and the speeds of the motor are obtained by strength analysis of the rotor structure.The electromagnetic force on the outer surface of the rotor calculated by the electromagnetic analysis is imputed into the strength analysis module.The influence of electromagnetic force on the strength of the rotor structure at different speeds is obtained.It is concluded that the optimized rotor structure meets the strength requirements.The vibration of the motor are calculated by establishing a coupling analysis model of electromagnetic field and structure field.The harmonic response analysis module is used to calculate the vibration and deformation of the motor,as well as the frequency spectra of the vibration velocity and acceleration.By establishing a spherical radiation analysis model,the sound pressure and sound pressure level of the sound field of the motor are calculated using the result of the vibration of the motor casing.The noise of the motor after optimization have been reduced 15.66 d B,which proves the effectiveness of the optimization method in reducing motor vibration and noise.