Stray flux and air gap flux experimental measurement and analysis in large hydro generators

This paper presents experimental measurement and analysis of both stray and air gap magnetic fluxes performed on various large hydro generators. The study shows the similarity and the differences of these two types of measurements when it comes to develop diagnosis method and remedial strategies. The radial and tangential components of the stray flux are also shown at different measurement points around the electrical machine. The study shows the usefulness of this measurement approach to detect electrical and mechanical faults found in large hydrogenerators such as rotor eccentricity (static or dynamic), rotor ellipticity and interturn short circuit in the rotor windings.