Eccentricity diagnosis in 2p-Pole alternators through superimposition of four 2(p±1)-pole virtual machines

The rotor eccentricity (RE) of synchronous generators (SGs) is assessed in this paper, through measurement of internal currents in stator windings with parallel loops. REs cause an airgap flux density amplitude modulation, resulting in four superimposed flux distributions with 2(p±1) poles in 2p-pole SGs, which correspond to four virtual rotors. The armature winding is decomposed through symmetrical components, which define two additional 2(p±1)-pole virtual armatures. Four fault-related 2(p±1) -pole virtual machines are so obtained, whose currents provide a good estimation of REs. Theory and simulations for a six-pole 1950kVA machine are provided in this paper. Simulations of the 1950kVA SG and tests on a four-pole 17kVA SG with regulated eccentric flange provided confirmation of the theoretical work.