Analysis of electromagnetic vibration in shaft generator application

Abstract

This master's thesis focuses on the analysis of electromagnetic vibration in a permanent magnet shaft generator when subjected to harmonics of the fundamental frequency excitation. Specifically, the study aims to understand the rotor lateral vibrations resulting from static and dynamic eccentricity. To achieve this, a comprehensive investigation is conducted using finite element modal and harmonic analysis on a full model employing solid elements. Mathematical models of harmonic forced vibration are also developed and validated using the finite element model. The research incorporates the analysis of experimental data, with a particular emphasis on key observation parameters. Through the application of both analytical techniques and the finite element method, the amplitude progression of the excitation force as a function of dynamic air-gap is estimated, and the amplitude of the one-time line frequency excitation at the resonance state is calculated. The influence of shaft deflection on dynamic air-gap variation is examined as well. Moreover, the study delves into the examination of the equivalent stiffness of the rotor line and its correlation with air-gap stiffness. By determining the minimum required stiffness, valuable insights into the system's behavior is obtained in which can be contributed to intermediate shaft design criteria.