Dynamic behavior of permanent magnet synchronous motor rotor bending fault

Abstract

Permanent Magnet Synchronous Motors (PMSMs) are increasingly utilized across various applications due to their high energy efficiency, power density, and precision. The research on the vibration characteristics associated with rotor bending eccentricity faults in PMSMs presents complexities in modeling; consequently, relevant findings in this area are limited. This paper investigates the effects of two fault conditions (Case1: misalignment of bearing inner ring tilt angle and rotor bending coupling fault, Case2: healthy bearing but rotor bending fault) on system vibration using the finite element method. This paper presents a model for the time-varying rotor center position, incorporating a mixed eccentricity unbalanced magnetic pull (UMP) model alongside a dynamic misalignment angle restoring force model for the bearing’s inner ring. Based on these components, a finite element dynamics model for the rotor-bearing system has been established. The Newmark-β method is employed to solve the multi-degree-of-freedom dynamic equations, enabling the acquisition of the vibration response of the motor rotor bending fault system. Furthermore, a comparative analysis of the dynamic responses for Case1 and Case2 is performed. Research indicates that as fault intensity increases, the amplitude of the frequency-doubled component rises significantly. Furthermore, bearing misalignment faults notably enhances the restoring force of the bearings. This enhancement, which in turn increases the support stiffness and effectively dampens the vibrations of the rotor in the normal direction. These findings hold significant value for fault diagnosis and the development of these systems.