| The fractional-slot concentrated-windings interior permanent magnet synchronous machine has a broad application prospect in the field of new energy vehicles because of its small size,high efficiency and simple topology.However,compared with the integer slot machine,the interior fractional-slot concentrated-windings permanent magnet synchronous machine has more serious vibration noise problem due to its own abundant magnetomotive force harmonics and low spatial order force waves generated by the near-pole slot combination,which greatly reduces the comfort of vehicle drivers and passengers.Thus,in this paper,a 24-pole 36-slot interior fractional-slot concentrated-windings permanent magnet synchronous generator for an extended-range electric vehicle is used as the research object,and the analysis and suppression technology of its electromagnetic vibration noise is carried out by the combination of analytical method and finite element method.The specific contents include the following:Firstly,for the problem that the source of electromagnetic vibration noise of interior permanent magnet synchronous machine is not clear and the influencing factors are complicated,we propose to establish the analytical model of air gap magnetic field of unslotted permanent magnet synchronous machine based on the theory of magnetic field periodicity,and obtain the analytical equation of radial and tangential magnetic field of interior permanent magnet synchronous machine by calculating the complex relative permeability function and the modulation effect of stator slotting effect and rotor saliency effect on air gap magnetic field.The analytical equations for the radial and tangential magnetic fields of the interior permanent magnet synchronous machine are obtained.Based on the Maxwell stress tensor method,the analytical equations of radial and tangential electromagnetic force waves are further derived to obtain the harmonic sources and characteristics of radial and tangential electromagnetic force waves under the effect of stator slotting and rotor saliency,which provide the theoretical basis for the subsequent electromagnetic vibration noise suppression.Secondly,for the problem that the stator system of automotive permanent magnet synchronous machine has complex structure assembly and low accuracy of modal analysis,the influence law of anisotropic material parameters on the stator core positive and negative phase modal frequencies is investigated,and the correction method of anisotropic material parameters is summarized.After the material correction,the simulated and tested values of the stator core and stator assembly free mode frequencies are within 2% and 4%respectively,which verifies the effectiveness of the anisotropic material parameter correction method.Then,the electromagnetic-structure-acoustic field multi-physics domain vibration noise simulation prediction model of the permanent magnet synchronous machine is established,and the electromagnetic force wave and electromagnetic vibration noise spectrum characteristics of the prototype under specific operating conditions are obtained,so that the main excitation force wave of the prototype is determined,and the harmonic sources of the main excitation force wave of the prototype are analyzed in combination with the analytical method.The vibration noise simulation method with separate loading of radial and tangential electromagnetic forces is used to quantitatively analyze the contribution of each directional electromagnetic force to the electromagnetic vibration noise,and to clarify the direction for the subsequent vibration noise suppression.The vibration noise test platform of the prototype is built to test the vibration noise level of the prototype,and there is good agreement between the test results and simulation results of the vibration noise spectrum.Finally,an auxiliary slot is proposed to suppress the electromagnetic vibration noise of the prototype.The influence laws between the parameters of the stator and rotor auxiliary slots on the 0th-order 6th-frequency radial force,the 0th-order 6th-frequency tangential force and the average torque are analyzed.In order to improve the optimization efficiency,sensitivity analysis is introduced to exclude the parameters that are not sensitive to the optimization objective,and the design of the auxiliary slot parameters is optimized based on multi-objective genetic algorithm.The electromagnetic performance and vibration noise level of the optimized scheme before and after optimization are compared and analyzed by finite element simulation,and the optimized scheme is verified experimentally. |
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