| Low speed and high torque electric spindle permanent magnet synchronous motor integrates the spindle and the spindle motor,eliminates the transmission system,realizes the direct drive of the motor,reduces the energy consumption and equipment manufacturing costs and maintenance costs.Now it has been widely used in various industrial fields,and has become one of the research hotspots in the field of motor,which has high scientific significance and practical value.However,there are some problems in the existing motors that affect the performance of the motor.In the low-speed high-torque electric spindle surface-mounted permanent magnet synchronous motor,in order to ensure the stability of the motor output torque and machining accuracy,it is necessary to suppress the torque ripple of the motor.In addition,because the low-speed and high-torque electric spindle permanent magnet synchronous motor adopts the design of a large inner diameter hollow shaft,the radial thickness of the rotor punching plate is relatively small,and the internal magnetic leakage of the rotor is large.This phenomenon is particularly significant under the interior permanent magnet excitation method.Therefore,in order to optimize the performance of the motor and ensure the high-precision operation of the motor,this paper studies the cogging torque and torque ripple under the surface mounted structure,and proposes a new structure for the rotor flux leakage problem under the interior permanent magnet structure and performs multi-objective parameter optimization.The main content of this article is analyzed in detail from the following aspects:1.The composition and generation mechanism of the torque ripple of the permanent magnet motor are analyzed by using the analytical method.First,the composition and mechanism of torque ripple are analyzed by establishing a mathematical model of the motor,and then the generation mechanism of cogging torque is analyzed.Finally,based on the energy method and Fourier decomposition,the cogging torque of the traditional surface-mounted permanent magnet motor is analyzed.2.Based on the magnetic pole parameters,the cogging torque of the low-speed high-torque electric spindle surface-mounted permanent magnet synchronous motor is studied,and the cogging torque under different magnetic pole structures is analyzed by classifying different magnetic pole models and combining the energy method.Using finite element software,simulation models are established to study the cogging torque under different magnetic pole models.The relationship between structural parameters of pole-cutting and combined magnetic poles and cogging torque is studied to obtain the optimized magnetic pole parameters.The effectiveness of pole-cutting and combined magnetic pole structures is verified by comparing other performance of the motor before and after optimization.3.The method of opening auxiliary slots on permanent magnets is proposed to reduce cogging torque.The equivalent model is used to simplify the auxiliary slot shape.The formulas of cogging torque under single and double rectangular slots are derived from the energy method,and the effect of the size of the auxiliary slot on the cogging torque is studied by using the finite element analysis software.The optimal size selection is determined,and the effectiveness of the method is verified by comparing the torque characteristics before and after the comparison.In addition,torque separation is performed on the rated torque of the motor based on the frozen permeability,the influence of each torque on the torque ripple is analyzed,and the harmonic content is offset by the method of injecting harmonic current to suppress the torque ripple of the motor.In addition,the rated torque of the motor is separated based on the frozen permeability method,and the degree of influence of each torque on the torque ripple is analyzed.The harmonic current injection method is used to offset the harmonic content and suppress the torque ripple.4.Aiming at the problems of high harmonic content of the air gap magnetic flux density and magnetic leakage inside the rotor in the low-speed high-torque electric spindle interior permanent magnet synchronous motor,a new type of non-uniform Halbach structure is proposed.The model is established to determine the design parameters,and the influence of each parameter on the air-gap magnetic density is analyzed.Taguchi method is used to optimize the multi-objective parameters of the motor,and the harmonic content of the no-load air-gap magnetic flux density and the fundamental wave amplitude are the optimization targets,the thickness of the permanent magnet,the angle of magnetization,the angle of the permanent magnet and the ratio of auxiliary magnetic pole are optimized parameters.The final optimization plan is determined,and the other performances of the motor before and after optimization are compared.This paper takes the low-speed and large-torque electric spindle permanent magnet synchronous motor as the research object,and conducts a comparative and systematic study on the generation and suppression of the motor torque ripple.Aiming at the problem of high torque ripple under the surface mounted structure,the suppression method based on magnetic pole parameters and harmonic current injection method are proposed,and the effectiveness of the method is verified by finite element analysis software.In addition,a new structure is proposed for the problem of high internal magnetic leakage of the rotor under the interior permanent magnet structure,and Taguchi method is used to optimize the design.The method adopted in this article is relatively simple and practical,which can provide references for the work of torque ripple suppression and multi-objective optimization design of permanent magnet motors. |
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