Abstract Modal analysis is an important part of motor vibration and noise analysis. To accurately obtain the results of motor modal analysis, it is necessary to assign corresponding elastic modulus parameters to the stator, armature winding, casing, end cover, and other structures. When the structural material is determined, its elastic modulus is also determined. Analytical and finite element calculations are based on ideal conditions, and there is often a significant error between the calculated and actual results based on the determined elastic modulus. The structure of the entire machine model, such as the casing and end cover, greatly affects the stator modal. For a finite element model, adjusting anisotropic parameters like the stator core and winding is necessary. At this stage, the determination of the elastic modulus of the motor structure is mainly done through modal experiments to adjust the parameters of the simulation results. Their errors converge to a reasonable error range. Although this method can obtain stator modal analysis results with high accuracy, the influence of parameter adjustment on each order of natural frequencies is not linear. Suppose its directionality cannot be clearly pointed out, it is difficult to adjust the parameters of the stator assembly and the entire machine. As a result, adjusting the errors of each order is difficult. Therefore, a double-stator electric-excitation field-modulated machine is taken as the research object. First, the initial values of the material parameters of each structure are determined, and the elastic modulus that affects its modal analysis is studied using finite element software. The relative influence rate of the elastic modulus changes in the outer stator, armature winding, casing, and end cover on each order of natural frequency is observed. According to the value relationship between elastic modulus, distinct adjustment methods were identified: three for the outer stator, four for the armature winding, and singular for the casing and end cover, thereby clarifying the directionality of elastic modulus adjustment for each structure. After that, the hammer method was used to conduct modal experiments on the outer stator, the outer stator assembly, and the entire machine. The error magnitude between modal experimental results and simulation results was obtained. Finally, the elastic modulus of the outer stator, armature winding, casing, and end cap was adjusted based on the error magnitude and the directionality for elastic modulus adjustments. Due to the complexity of the entire machine’s structure, it is necessary to appropriately equate the motor structure before adjusting the elastic modulus. It is found that modifying the elastic modulus of the outer stator, casing, and equivalent end cover has a similar effect on the natural frequencies across various orders of the entire machine. The effects on the 2nd and 3rd orders are significantly greater than the 4th order, and the armature winding has an opposite effect. Therefore, according to the error between the finite element modal analysis and experimental results obtained with the initial elastic modulus, the elastic modulus adjustment values for the outer stator and armature windings, determined through modal experiments, are selected. The elastic modulus of the casing and end cover is directly adjusted to minimize errors. The error of the finite element modal analysis results for the entire machine is within 4%. It proves that the proposed elastic modulus adjustment method can obtain more accurate modal analysis results for the entire machine, thereby facilitating the electromagnetic noise prediction and analysis of the motor.
Song Chuntong,Wang Yubin. The Elastic Modulus Adjustment Method of Double-Stator Electric-Excitation Field-Modulated Machine Based on Modal Analysis[J]. Transactions of China Electrotechnical Society, 2024, 39(6): 1713-1724.
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