| The permanent magnet synchronous motor(PMSM)is widely used in aerospace,national defense,industrial and agricultural production,and daily life due to its advantages such as small size,high efficiency,and high power density.With the continuous improvement of motor performance,the requirement for the comprehensive performance of PMSM is also increasing,and the vibration and noise performance has become an important indicator to measure the comprehensive performance of PMSM.Especially in some high-speed and high-power applications,the vibration and noise problems of PMSMs are very prominent,which seriously affect the reliability of the motor system and are one of the key issues that urgently need to be solved.The electromagnetic vibration excited by electromagnetic force waves is the main source of vibration and noise in PMSM.Especially for PMSMs powered by inverters,the electromagnetic force waves generated by the rich current harmonics will aggravate the electromagnetic vibration of the motor.At the same time,the wide range of speed variation of PMSMs powered by inverters results in a wide range of the frequency of the electromagnetic force waves,the frequency of the electromagnetic force waves is difficult to avoid the natural frequencies of the stator of PMSMs,which makes it more difficult to suppress the electromagnetic vibration of the motor.At present,domestic and foreign scholars have made good research progress in the electromagnetic vibration of PMSMs,but there are still many shortcomings in the calculation methods of electromagnetic force waves and stator natural frequency,as well as the comprehensive weakening measures of electromagnetic vibration,mainly reflected in:The existing calculation methods of electromagnetic force waves can not accurately determine the complete expression of each electromagnetic force wave,including amplitude,order,and frequency.In addition,a fast and accurate calculation method of the stator natural frequencies that can accurately consider the complex structural parameters of the stator and the impact of the end cover is missing.It is necessary to summarize the general weakening measures of electromagnetic vibration of PMSMs powered by inverters from a system perspective.In view of these,relying on the key project of the National Natural Science Foundation of China under grant 51737008 of "Research on Key Basic Problems of Electromagnetic Vibration of Permanent Magnet Synchronous Motors Powered by Inverters",this paper conducts in-depth research on the key basic problem of the calculation,analysis,and weakening of electromagnetic vibration of PMSMs powered by inverters.The main research work is summarized as follows:(1)A fast and accurate calculation method for electromagnetic force waves of surfacemounted permanent magnet synchronous motors(SPMSMs)powered by inverters by combining subdomain method with magnetomotive force(MMF)-permeance methodThe existing methods for calculating electromagnetic force waves cannot accurately determine the complete expression of electromagnetic force waves including amplitude,order,frequency,and phase,which is not conducive to the analysis of electromagnetic force waves and the weakening of electromagnetic vibration.In response to the above shortcomings,this paper proposes a fast and accurate calculation method for electromagnetic force waves of SPMSMs by combining the subdomain method and the MMF-permeance method.Based on the subdomain method,the slotless and slotted stator models of SPMSMs are solved for no-load operating conditions,and the no-load air-gap MMF and air-gap permeance of SPMSMs are quickly obtained.Afterward,based on the MMF-permeance method,the no-load air-gap flux density of the motor is calculated.Furthermore,the Maxwell stress tensor method is used to solve the no-load electromagnetic force waves of the motor,and the complete expression of the no-load electromagnetic force waves is quickly and accurately obtained.Considering the harmonics of the rotor magnetic field,this paper establishes a mathematical model of SPMSMs powered by inverters,the winding currents are obtained,and the armature MMF is calculated based on the calculation model of armature MMF.Next,the permeance calculation model of the armature MMF acting alone is solved based on the subdomain method to obtain the air-gap permeance when the armature MMF acts alone.Finally,the armature magnetic field is calculated using the MMF-permeance method,and it is superimposed with the no-load air-gap magnetic field to obtain the air-gap flux density and the electromagnetic force wave with the rated load of the motor.(2)A fast and accurate calculation method for electromagnetic force waves of interior permanent magnet synchronous motors(IPMSMs)powered by inverters by combining FEM with MMF-permeance methodAccurately considering the complex rotor structure of IPMSMs,this paper proposes a fast and accurate calculation method for electromagnetic force waves of IPMSMs,which combines the FEM with the MMF-permeance method.For the no-load working condition,two finite element simulations are conducted on the slotless stator model and the slotted stator model of the IPMSM,to accurately obtain the no-load air-gap MMF considering the complex structural parameters of rotor,as well as the air-gap permeance coefficient caused by stator slotting.The MMF-permeance method is used to calculate the air-gap flux density and the electromagnetic force waves of the motor.Afterward,the rated current of the IPMSM when using the control method of maximum torque per ampere(MTPA)is calculated,and the armature MMF of the motor is calculated based on the armature MMF calculation model.On the basis of freezing the magnetic permeability,the permanent magnets(PMs)in the rotor slot are set to air,and the position of the virtual PMs in the air gap is adjusted to make the magnetic pole centerline coincide with the d-axis or q-axis of the rotor.Three finite element simulations are conducted on the structural model before and after the rotor slotting,and the d-and q-axes air-gap permeance coefficients caused by the rotor slotting and the saturation of the magnetic bridges are obtained.Finally,the MMF-permeance method is used to calculate the air-gap flux density of the motor,and the electromagnetic force waves of the motor with rated load are further obtained by the Maxwell stress tensor method.The analysis shows that rotor slotting and the saturation of the magnetic bridges in IPMSMs have a significant impact on the d-axis component of the armature fundamental MMF,while their impact on the q-axis component and harmonic MMFs is minimal.Compared with directly using the FEM to analyze the electromagnetic force waves of IPMSMs,the method proposed in this paper can greatly shorten the calculation time,clarify the specific sources of each component of the electromagnetic force wave,and facilitate the calculation and weakening of electromagnetic vibration.(3)A fast calculation method for stator natural frequency considering the complex structural parameters,anisotropic material parameters,and effects of end coverThe existing analytical calculation methods for stator natural frequencies simplify the stator structure,and the accuracy of the calculation results is low;the finite element method has the drawbacks of large modeling workload and long calculation time.In response to the shortcomings of the existing analytical method and FEM in stator natural frequency calculation,this paper proposes a fast and accurate calculation method for stator natural frequency based on the energy method.Firstly,an accurate equivalent model of the stator,including the stator core,winding,and casing,is established.The stator core and casing are equivalent to cylindrical shells with additional axial ribs inside and outside the shells,respectively.Considering the orthogonal material characteristics of the laminated core and equivalent windings,a method for determining the orthogonal anisotropic material parameters of the stator core and windings is proposed based on the composite material parameter calculation method.Based on the accurate equivalent model of the stator,the energy method is used to derive the natural frequency characteristic equation of the stator under free boundary conditions.Based on the composite shell theory,the analytical calculation model of the natural frequency of the composite shell composed of the stator core and casing is further improved.Compared with the results obtained by FEM and prototype testing,the method proposed in this paper can accurately consider the mass and stiffness of various parts of the stator,and the calculation results have high accuracy.Finally,the influence of stator structural parameters on its natural frequencies is analyzed,which lays a theoretical foundation for the adjustment of stator natural frequencies and the suppression of electromagnetic vibrations.(4)Fast calculation method of electromagnetic vibration based on the linear superposition principleIn response to the shortcomings of existing electromagnetic vibration calculation methods that cannot balance speed and accuracy,this paper proposes a fast calculation method for electromagnetic vibration.Firstly,the distributed electromagnetic force density acting on the surface of the stator teeth is equivalent to the concentrated electromagnetic force acting on the teeth with the same effect.Considering the influence of tangential electromagnetic force,the mechanism of 0-order and low-order electromagnetic forces on electromagnetic vibration is analyzed in depth,and the electromagnetic force components that play a major role in electromagnetic vibration are summarized.The analysis shows that for a 6-pole 36-slot PMSM,the 0-order radial electromagnetic force,6-order radial electromagnetic force,and 6-order tangential electromagnetic force in the motor have the greatest impact on electromagnetic vibration.Then,the frequency response function of each stator mode is calculated based on the unit force response,and the no-load electromagnetic vibrations of SPMSM and IPMSM are quickly calculated according to the linear superposition principle of electromagnetic vibration.Although there are some errors between the results obtained by the linear superposition method of electromagnetic vibration and the finite element results and prototype test results,it can still accurately reflect the distribution law of the stator vibration acceleration spectrum,which is of great significance for the rapid prediction of electromagnetic vibration and the grasp of electromagnetic vibration laws.(5)Effective weakening measures for electromagnetic vibration of PMSMsAccording to the characteristics of the PMSMs powered by inverters,the coincidence law of the electromagnetic force waves and stator natural frequencies is studied in depth,and the general electromagnetic vibration weakening measures of the PMSMs powered by inverters are summarized.Starting from the perspective of weakening the amplitudes of electromagnetic force wave components that play a major role in electromagnetic vibration,this paper proposes some comprehensive weakening measures for electromagnetic vibration of PMSMs based on segmented magnetic poles,different combinations of pole-arc coefficients,unequal thickness magnetic poles,unequal tooth widths,unequal slot widths,and opening auxiliary slots.A universal method for selecting stator and rotor structural parameters is provided,and the weakening effect of electromagnetic vibration is analyzed and verified by the FEM and prototype testing.A multi-objective hierarchical optimization method for IPMSMs with complex rotor structures is proposed,which combines the FEM and the improved iterative Taguchi method,and the electromagnetic vibration of the motor are effectively reduced.Compared with the traditional Taguchi method,the improved iterative Taguchi method proposed in this paper can greatly improve optimization efficiency while ensuring computational accuracy.In response to the inevitable rotor eccentricity in the motor,this paper proposes a winding connection method with additional voltage-sharing lines.Based on the FEM,the electromagnetic vibration of a 6-pole 36-slot SPMSM with rotor eccentricity is analyzed under different winding connection methods.The results show that the winding connection method proposed in this paper can effectively weaken the electromagnetic vibration caused by rotor eccentricity.Finally,the weakening measures of high-frequency electromagnetic vibration using random switching frequency and increasing switching frequency are deeply analyzed to improve the electromagnetic vibration near the switching frequency of the PMSMs powered by inverters. |
PDF Full Text Request