Abstract
Theoretical analysis and numerical FEM calculations, together with segmental experiment studies, are used to study the impact of the static air-gap eccentricity forms on the rotor unbalanced magnetic pull (UMP) of turbogenerator. The universal expression of the magnetic flux density under different forms of SAGE is firstly deduced, based on which the detailed UMP formulas for the normal condition and three SAGE cases are obtained, respectively. Then the exciting characteristics of the UMP for each SAGE form to generate vibrations are analyzed. Finally, numerical FEM calculations and segmental experiments are carried out to investigate the effect of SAGE forms on the rotor UMP, taking the SDF-9 type non-salient-pole fault simulating generator as the object. It is shown that, no matter what kind of SAGE occurs, amplitude increments at each even harmonic component of the UMP and the rotor vibration, especially the 2nd harmonic component, will be brought in. Meanwhile, the UMP keeps directing to the very position where the minimum radial air-gap is. Among the different SAGE forms, the rotor offset has the most sensitive effect on the rotor UMP and vibration, while the stator ellipse deformation has the weakest impact.
Highlights
Due to the assembly quality, the bearing damage, and the performing environments, most generators are running under an air-gap eccentricity condition [1]
The intent of this paper is to investigate the impact of static air-gap eccentricity (SAGE) forms, including rotor offset, stator concave deformation, stator convex deformation, stator ellipse deformation, and mixed SAGE composed of rotor offset and stator deformation, on the rotor unbalanced magnetic pull (UMP) characteristics
We mainly focus on the effect of the SAGE forms on the rotor UMP; the refined analysis about the formula simplification error will not be taken due to the space limitation
Summary
Due to the assembly quality, the bearing damage, and the performing environments, most generators are running under an air-gap eccentricity condition [1]. The air-gap eccentricity, which is usually named as rotor eccentricity by many scholars, appears as the air-gap is larger on one side but smaller on the other side. The bearing offset or the stator core deformation can cause a typical static airgap eccentricity [2]. A very tiny air-gap eccentricity will not bring in serious impact on the generator’s regular performing. When the eccentricity degree is more than 10% of the total air-gap length, severe vibrations, stator core deformations, and even winding damage will be caused [3]. Accurate monitoring and timely control on this kind of fault is of significance
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