Vibration characteristic analysis of rotor rub-impact fault under air-gap mixed eccentricity of motor

Abstract

The air gap eccentricity fault of the motor will cause the distortion of the air gap magnetic field of the motor, so that the resultant force of the magnetic pull on the rotor circumferential direction is not zero, and the resultant force is unbalanced magnetic pull. Unbalanced magnetic pull will aggravate the vibration of the motor rotor, and even cause rub-impact fault between the rotor and stator, which will affect the safe and stable operation of the motor. In this paper, a rotor rub-impact fault model with air-gap mixed eccentricity is established, and then the rotor dynamic equation is solved by numerical simulation. The dynamic characteristics of the rotor under different fundamental MMF (Magnetic Motive Force) are compared by time domain waveform, spectrum, axis trajectory, Poincare map and bifurcation diagram. The results show that there is no rub-impact fault in the rotor system at low speed, and the unbalanced magnetic pull will make the rotor produce zero frequency, fundamental frequency and second harmonic components; with the increase of rotating speed, rub-impact fault occurs in the rotor system. At this time, the existence of unbalanced magnetic pull enhances the nonlinear characteristics of the rotor.