Nonlinear vibration of a generator rotor with unbalanced magnetic pull considering both dynamic and static eccentricities

The nonlinear vibration of the rotor with unbalanced magnetic pull (UMP) has been extensively investigated in the literature. Most of them focused on the calculation of UMP considering only dynamic eccentricity, while the static eccentricity was generally ignored in current studies. Static eccentricity is actually inevitable due to many reasons. This paper aimed to study the nonlinear responses of a rotor with dynamic and static eccentricities (DSE). The air-gap length unified formula considering DSE is established, and the UMP of the rotor system is obtained by numerical method. The vibration characteristics of a UMP excited rotor with only dynamic eccentricity and DSE are, respectively, discussed in detail for comparison. The effects of rotating frequency and initial static eccentricity on rotor shaft orbit and displacement spectra are acquired. Results illustrate that dynamic behaviors of the UMP excited rotor with DSE are different from those of the rotor with only dynamic eccentricity. The rotor shaft orbit is axis symmetry rather than central symmetry, and the rotor is more likely to have contact with the stator in the direction of static eccentricity. Zero and double supply frequency always exists in the frequency components of the displacement. Not only two and four times of the rotating frequency harmonic appear, but also double supply frequency plus one and two times of rotating frequency harmonic are discovered.