Abstract
Accurate calculation on circumferential natural frequencies of stator structure in permanent magnet synchronous motor (PMSM) is very important for predicting the vibration and noise of PMSM. The analytical modal formula for the stator structure in PMSM is proposed, starting from the mathematical displacement model of cylindrical shell, then deriving the analytical formula for the stator structure. Firstly, finite element method (FEM) is applied to analyze the circumferential natural frequencies of cylindrical shells with different length, wall thickness, mean diameter, diameter-thickness ratio, size and installation position of terminal box. The influences on circumferential natural frequencies of cylindrical shells are studied. Furthermore, a new analytical formula considering diameter-thickness ratio for calculating circumferential natural frequencies of cylindrical shells is developed. Compared with the results of FEM, the correctness of the analytical formula is verified. Then, novel analytical formulas considering stiffness errors are proposed to calculate the circumferential natural frequencies of stator core and motor case. Compared with the results of FEM, the effectiveness of analytical method is validated. Finally, a new analytical formula considering diameter-thickness ratio, stiffness errors, existence of terminal box and mutual constraints is presented to calculate the circumferential natural frequencies of stator structure. Compared with the results of FEM and experimental method, the relative errors are respective within |4.43 %| and |3.38 %|. The validity of analytical formula is confirmed.
Highlights
As compared to other motors, due to their high power density, good dynamic performance and high energy conversion efficiency, permanent magnet synchronous motors (PMSMs) have been more and more widely used in many fields, such as home appliances, machine tools, automobile, military and other fields [1, 2], but there are still many problems to be solved
This paper investigates the calculating method for the circumferential natural frequency of stator in PMSM
Through the analysis on the influence of length, wall thickness, mean diameter, diameter-thickness ratio, size and installation position of terminal box on the circumferential natural frequencies of cylindrical shells, the influence of stator core and motor case simplified as cylindrical shells on their circumferential natural frequencies, and calculation for the circumferential natural frequencies of stator structure with analytical method, finite element method (FEM) and experimental method, the following conclusions can be obtained: 1) The length of cylindrical shells has little influence on their circumferential natural frequencies, which can be neglected in calculation
Summary
As compared to other motors, due to their high power density, good dynamic performance and high energy conversion efficiency, permanent magnet synchronous motors (PMSMs) have been more and more widely used in many fields, such as home appliances, machine tools, automobile, military and other fields [1, 2], but there are still many problems to be solved. The influence of wall thickness and other parameters on the circumferential natural frequencies of cylindrical shells and the calculating results of different formulas are analyzed in this paper. Compared with the results of Hoppe theory and Donnel-Mushtari theory, the improved analytical formula for calculating circumferential natural frequencies of cylindrical shells is obtained. The circumferential natural frequencies of stator core and motor case which are simplified into cylindrical shells are calculated. The circumferential natural frequencies of stator structure are calculated by analytical method, FEM and experimental method.
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