Static and dynamic rotor eccentricity on-line detection and discrimination in synchronous generators By No-Load E.M.F. space vector loci analysis

In this paper a study about the different effects of static and dynamic rotor eccentricities on the external electric variables of a salient-pole synchronous generator is presented. Air-gap irregularities and related monitoring techniques have been studied in the past mainly about large hydro-generators (with practical applications), but similar problems have been recognized for on-board ship synchronous generators. These latter require a different approach, i.e. non-invasive monitoring. Static and dynamic rotor eccentricities were simulated in this work, for a ship-application sized generator, by using a dynamic model including inductances computed by parametric 3D FEM analysis of the faulty machine. Current, voltage, and no-load e.m.f. steady-state waveforms were analyzed by FFT and space-vector approach. No-load e.m.f. space vector is a sensitive fault indicator since its amplitude largely increases with the level of absolute eccentricity; furthermore, it is possible to discriminate the static eccentricity from the dynamic eccentricity utilizing the space vector loci ovality.