Rotor eccentricity evaluation in an alternator with parallel pole-phase-groups in the stator: FEM simulations and experimental proofs

This paper shows a method for rotor eccentricity (RE) evaluation in synchronous machines (SMs) by measurement of internal currents in stator windings with parallel connections. REs produce a space/time air gap flux amplitude modulation, resulting in additional 2(p±1)-pole flux distributions in 2p-pole SMs. The correspondent internal reaction currents are translated in the complex domain by a Fortescue´s space-transformation. 2(p±1)-pole current space vectors trace epitrochoidal trajectories, and provide an affordable estimation of static and dynamic REs. Practical formulas were carried out for RE assessment, which require few machine parameters. Experiments were performed on a 17kVA SM with regulated eccentricity and reconfigurable stator windings. The results are compared with those obtained through transient time-stepping FEM simulations.