| In recent years,the permanent magnet synchronous motors(PMSMs)have shown spacious application prospects in industrial production,commercial electrical appliances and aerospace fields due to their simple structure,high efficiency and high power density.With the continuous improvement of the motor manufacturing process and the continuous improvement of the performance of PM materials,people have higher and higher requirements for the performance of PMSM.The vibration and noise of PMSMs have become an important factor in measuring their performance.As a main component of the vibration and noise of PMSMs,the electromagnetic noise is derived from electromagnetic vibration and is excited by the electromagnetic excitation force wave acting on the stator core by the air gap magnetic field of the motor.Therefore,The analysis and the study of weakening measures of electromagnetic vibration and noise are crucial.The accurate expression of electromagnetic exciting force waves becomes the key to electromagnetic vibration analysis and calculation.Starting from the source of motor vibration and noise,the electromagnetic exciting force waves in surface-mount permanent magnet synchronous motor(SPMSM)are analyzed and calculated in detail,and the weakening measures are studied.The main works and the results are as follows:1.Fast and Accurate Calculation and Analysis of Electromagnetic Exciting Force Waves of SPMSMAiming at the shortcomings of the finite element method(FEM)and magnetomotive force(MMF)-magnetic permeability method in the calculation of electromagnetic exciting force waves,this paper proposes a fast and accurate calculation method of electromagnetic exciting force wave.For the no-load magnetic field,the MMF generated by PM and the air-gap magnetic permeability are calculated by the twice finite element simulation.The expression of no-load MMF and air-gap permeability including amplitude,frequency and phase can be obtained by Fourier decomposition.For the armature magnetic field,the equivalent magnetic permeability prediction model is established by using the method of freezing magnetic permeability,the air-gap permeability and harmonic contents of the armature when acting alone are obtained.The MMF of the winding is multiplied by the air-gap permeance to obtain the air-gap flux density under the action of the winding alone.Finally,the air-gap under the action of the PM and the armature winding is superimposed to obtain the air-gap flux density on load of the motor.At the same time,the obtained PM and armature MMF and air-gap permeability components are substituted into the MMF-permeability equation for solving the electromagnetic exciting force wave,and the force wave amplitude at a specific frequency and order can be accurately obtained.Finally,the accuracy of the fast and accurate calculation method is verified by the FEM.The method can quickly and accurately obtain the amplitude of the electromagnetic excitation force wave of a specific order,which facilitates the weakening.2.Influence of Stator and Rotor Structure Parameters on Electromagnetic Exciting Force WavesBased on the two affecting factors of the order and the amplitude of the electromagnetic exciting force wave,the influences of the stator and rotor structure parameters on the electromagnetic exciting force wave are analyzed in detail.Firstly,considering the smaller the vibration deformation,the smaller the force wave order,the minimum force wave order in the conventional PMSM is deduced,and the electromagnetic exciting force wave order in the motor with different pole-slot combination is analyzed.The influence of the auxiliary slot on the electromagnetic wave order of the fractional-slot PMSM is studied.Secondly,taking the electromagnetic force wave of the SPMSM as an example,the influence of the stator slot opening width,tooth width/pitch,skewed-slot and pole-arc coefficient,magnetization mode,magnetic pole block number,magnetic pole eccentricity and rotor eccentricity on the MMF of the PM and air-gap permeability under no-load conditions.The changing law of electromagnetic exciting force wave is verified by the FEM,which provides a theoretical basis for the weakening of the electromagnetic exciting force waves and even the electromagnetic vibration.3.Analysis of Electromagnetic Exciting Force Wave of PMSM with Inverter Power SupplyConsidering that the armature current in the actual operation of the motor contains harmonic components inevitably,especially when using the inverter power supply mode,the high-order harmonic components near the switching frequency and its integer multiple are very rich.The electromagnetic excitation force wave at the time of the wave current is analyzed and calculated in detail.Firstly,the harmonic contents of the armature current under the actual three-phase sinusoidal voltage supply is simulated and analyzed,and the newly introduced electromagnetic exciting force wsave are summarized.Then,based on Matlab/Simulink software,the id=0 vector control circuit of the motor is built,and the output current harmonics of the inverter and the electromagnetic exciting force wave generated by voltage space vector pulse width modulation are analyzed and verified by FEM,make preparation for the analysis of the vibration characteristics of the motor under the inverter power supply.Aiming at the current harmonics near the switching frequency introduced when the inverter is powered,the practical the weakenin measures of high-order harmonic such as improving the switching frequency of the inverter,and selecting the appropriate modulation method are analyzed,and the weakening effects are compared and the rationality of these methods are verified.4.Strength and Vibration Characteristics Analysis of Stator and Rotor under Electromagnetic Exciting Force WavesWhen the electromagnetic exciting force wave frequency is close to the natural frequency of the motor,it is easy to resonate and aggravate the electromagnetic vibration and noise of the motor.Therefore,this paper analyzes the natural frequency and vibration characteristics of the motor.Before calculating the natural frequency of the stator of the motor,the ANSYS Workbench is used to compare the changes of the stator and rotor stress under the electromagnetic exciting force wave to ensure the stability of the structure.After that,the three-dimensional dynamic analysis model of the stator core is established,and the free modal is analyzed to obtain the modal shape of the stator and its natural frequency.Then The electromagnetic excitation force wave under inverter power supply at rated load are applied as a load to the stator structure model,and the electromagnetic vibration such as vibration displacement and vibration acceleration of the stator is obtained.Finally,the variation law of stator natural frequency with yoke thickness and tooth width is studied,which provides a theoretical basis for reasonable adjustment of natural frequency and avoiding motor resonance. |
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