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In this paper a study about the different effects of static and dynamic rotor eccentricities on the external electric variables of a brushless salient-pole synchronous generator (SG) is presented. Air-gap irreularities and related monitoring techniques for synchronous machines have been studied in the past mainly about large vertical hydro-generators , but similar issues have been recently recognized as worthy of attention for on-board ship generators. Static and dynamic rotor eccentricities were simulated in this work, for a medium power ship brushless generator, by using a dynamic model including inductances computed by parametric 3D FEM and MWFA-based analyses of the faulty machine, and taking in account the damping effect of the parallel paths inside the machine. Currently voltage, and no-load e.m.f. sleady-state waveforms were analyzed by FFT. No-load vollage harmonics are sensitive fault indicators, whose harmonic content directly reflects level and type of eccentricity, and which can be used ror diagnostic purposes.