Static eccentricity detection in synchronous generators by field current and stator Voltage Signature Analysis - Part I: Theory

Static eccentricity detection can be performed by measurement of a double fundamental frequency ripple in the rotor current of synchronous machines. The ac ripple leads to clear signatures in the no-load terminal voltage spectra, pushing up some voltage harmonics normally smaller in the healthy machine. Rotor current ac ripple and related voltage harmonics can be used for diagnosis, since they are sensitive fault indicators. In Part I of this work, general criteria to preview the fault-related voltage harmonics for no-load machines affected by static eccentricity are carried out, based on the analysis of the winding structure. Simulations performed by using a winding function-based model, which takes in account the field shape in the inter-pole regions, confirm the theoretical predictions. In Part II, a 15kVA generator with regulated flange has been used for experimental validation with various eccentricities.