Research On Mechanism And Weakening Method Of Pole-frequency Vibration Of Surface-mounted Permanent Magnet Synchronous Motors With Similar Number Of Poles And Slots

The surface-mounted permanent magnet synchronous machines(PMSMs)with similar number of poles and slots are the most attractive candidates for the use as the power sources for military equipment fields such as electric propulsion ships and underwater vehicles due to its sample structure,inherent high efficiency and high power density.However,as an essential performance for the underwater military equipment,concealment is vulnerable to low-frequency vibration and noise of SPMSMs.The vibration and noise of the motor are caused by a series of electromagnetic force waves acting on the stator teeth.Among these excitation sources,the pole-frequency excitation source is the strong component,which leads to that the pole-frequency vibration is common and significant in PMSMs with different combines of pole and slot number.So far,numerous studies have been done on the pole-frequency of the surface-mounted PMSMs with similar number of poles and slot.However,there are still some deficiencies in the analysis method,type,fluctuation reason and weakening method of the pole-frequency exaction sources.In this dissertation,a model improved one-dimensional magnetic field analysis method is used to analyze the exaction source types and fluctuation reason of the pole-frequency vibration.On this basis,two effective weakening methods are proposed.Based on the excitation modes of radial and tangential force waves,a model improved one-dimensional magnetic field analysis method is proposed,and the contribution of two force waves to the pole-frequency vibration is compared.Firstly,based on the geometric model of teeth and yoke,the excitation modes of radial and tangential force waves are obtained.Then,a model improved one-dimensional magnetic field analysis method is proposed,and the excitation sources are equivalent to radial concentrated force and tangential moment.The tangential moment is solved by the energy method,which makes up for the deficiency that one-dimensional magnetic field method can not analyze tangential force wave.Based on the finite element model,the contribution of two force waves to the pole-frequency vibration are analyzed.The results show that both radial and tangential force waves are important pole-frequency excitation sources,and the contribution of tangential electromagnetic force to vibration is comparable to that of radial electromagnetic force.Considering the interaction of radial and tangential fore waves,the mechanism of the pole-frequency vibration is analyzed.Firstly,the relationship between the variation trend of excitation sources and the position of the magnetic poles on no load is analyzed.Based on the calculation process and formation mechanism of radial concentrated force and tangential moment,the causes of the pole-frequency vibration on no load are determined.Then,the variation trend of excitation sources and the distribution characteristics of flux density in two conditions are compared to verify the validity of conclusions obtained.The results show that the magnetic field distortion caused by the zero-crossing region is the main cause of the pole-frequency vibration.An axial symmetrical piecewise stagger unequal pole structure is proposed,and its weakening effect on the pole-frequency vibration is analyzed.Firstly,a finite element model is established to revel the weakening mechanism of this structure.Then,the vibration experiment is set to verify the validity of this structure.In addition,the axial symmetrical piecewise stagger unequal pole structure is compared with interpole magnetic pole structure.The results show that the axial symmetrical piecewise stagger unequal pole structure can effectively reduce the pole-frequency vibration while ensuring the torque density.Compared with the interpole magnetic pole scheme,the axial bending moment is eliminated and torque ripple is reduced for the axial symmetrical piecewise stagger unequal pole structure.On the basis of the axial symmetrical piecewise stagger unequal pole structure,an axial symmetrical piecewise stagger trapezoidal pole structure is proposed.Different from the axial symmetrical piecewise stagger unequal pole structure,the adjacent edges of the pole of the structure are continuously skewed.Firstly,the finite element model of this structure is established,and the flux density distribution characteristics and the variation of the excitation sources are analyzed,which reveals the weakening mechanism of this structure on the pole-frequency vibration.Then,based on the harmonic response analysis and experiment results,the effectiveness of this structure is verified.In addition,the axial symmetrical piecewise stagger trapezoidal pole structure is compared with the axial symmetrical piecewise stagger unequal pole.The results show that compared with the axial symmetrical piecewise stagger unequal pole scheme,the acceleration level of the axial symmetrical piecewise stagger trapezoidal pole structure decreases,but the torque ripple increases.