Vibration Performance of a Three-Phase Asynchronous Motor With Air-Gap Eccentricity

In this paper, the vibration performances of a three-phase asynchronous motor with air-gap eccentricity were studied. The governing equations of the eccentric rotor-bearing system was established by considering the nonlinear bearing contact forces and the unbalanced magnetic pull (UMP) acting on the rotor. The UMP was calculated at the axial position of the supporting bearings, by integrating the total air gap distribution along the axial and circumferential direction. The air gap distribution can be deduced from the stator, rotor MMF harmonics and their related harmonics. By substituting the UMP into the governing equations, numerical responses of the rotor-bearing system under air-gap eccentricity can be simulated. Results show that the shaft orbits at both two ends of the shaft reside on their eccentric positions, i.e., the orbits of two shaft ends with symmetric angular eccentricity have the opposite phase direction. Besides, in the power spectrum of the simulated acceleration, the second harmonic component turns out to be notable compared with the fundamental frequency