UMP and Vibration Analysis for Eccentricity Detection in Permanent Magnet Synchronous Generators

This article investigates the unbalanced magnetic pull (UMP) and vibration characteristics in permanent magnet synchronous generators (PMSGs) under different types of air-gap eccentricity (AGE), including static eccentricity (SE), dynamic eccentricity (DE), and mixed eccentricity (ME). A novel experimental platform is designed to emulate various eccentricity conditions. Using the analytical modeling and finite-element analysis (FEA), the distinct UMP profiles are derived for SE, DE, and ME, and their effects on rotor vibration behavior are analyzed. Furthermore, the research reveals a direct correlation between UMP and spatial orientation of eccentricity faults. Experimental validations are conducted on a prototype generator, verifying the proposed analysis and highlighting the potential for eccentricity diagnosis using UMP and vibration features. It is shown that the spatial distribution of the UMP is point-like under SE, with its position corresponding to the location of the minimum air gap. The UMP distribution is circular under DE, with the position of the minimum air gap varying over time. In the case of ME, the UMP distribution forms an elliptical shape, and the center of this spatial distribution shifts toward the SE direction as the level of SE increases. Meanwhile, in the rotor vibration spectra, the dominant frequency component under SE is twice the electrical frequency (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2f$ </tex-math></inline-formula>). Under DE, the dominant component is the mechanical rotational frequency (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{r}$ </tex-math></inline-formula>). In ME, the vibration spectrum contains multiple frequency components, including <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{r}$ </tex-math></inline-formula>, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2f_{r}$ </tex-math></inline-formula>, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3f_{r}$ </tex-math></inline-formula>. These findings provide a useful reference for the monitoring and diagnosis of AGE.