Research On Electromagnetic Vibration Of Low-power Permanent Magnet Synchronous Motor

Permanent magnet synchronous motors,with the advantages of high efficiency,high power density,low torque ripple,simple structure,and significant energy saving effect,are enjoying a widespread application.However,the quality of relative product is limited by vibration and noise of the motor,and meanwhile the users' comfort requirement for motor products are getting higher and higher.Therefore,to enhance their competitiveness,measures must be taken to reduce the vibration and noise of the motor in terms of improving the quality of motor products and satisfying people's demands of the product.The research object in this thesis is a 25kW,8-pole,48-slot permanent-magnet synchronous motor.Firstly,a two-dimensional field-circuit coupled model of the motor is established.The finite element method is used to analyze and calculate the two-dimensional electromagnetic field under no-load conditions of the motor and the magnetic flux density of the radial and tangential air gaps in the gap path is extracted to calculate the radial electromagnetic force acting on the inner surface of the stator tooth,and the main order and its corresponding frequency of the calculated radial electromagnetic force are analyzed.At the same time,in order to study the influence of the motor structure parameters on the radial electromagnetic force,the electromagnetic fields of motor models of different air gaps,pole-slot combinations,thicknesses of permanent magnets,pole-arc coefficients and stator slot shape are simulated and analyzed.The results of their different influence on the radial electromagnetic force can provide references for subsequent motor design.Secondly,a three-dimensional model of permanent magnet synchronous motor is established.The free vibration of this motor without external load is analyzed in the modal superposition method to determine the corresponding natural mode frequency under different vibration modes of the motor structure.And the first six modes of vibration modes and their corresponding modal frequencies of the different structures of the motor stator system are studied to compare with the principal force waves order of the mentioned radial electromagnetic force and their corresponding frequencies.Thus given modal frequencies in each orders of a new motor design that differs from the frequencies of the main order of the radial electromagnetic force,the possibility that the radial electromagnetic force causes the motor to resonate is effectively decreased,and hence the motor's vibration and noise is reduced.Then,a three-dimensional dynamic model of a permanent magnet synchronous motor is established.The radial electromagnetic force is imposed to the inner surface of the stator tooth by means of finite element analysis,and the motor stator system model's vibration response under radial electromagnetic loading is obtained to calculate the frequency when the vibration acceleration is considerably large.And the data is verified through a comparison with the result of modal analysis.Finally,the effectiveness of theoretical analysis and simulation results is validated through a vibration test of permanent magnet synchronous motor,and the electromagnetic noise is calculated by analytical method.