Study of cardioid-shaped loop current space vector trajectories for rotor eccentricity detection in power synchronous machines

This paper studies the reaction currents of a synchronous machine (SM) with general rotor eccentricity (RE) and parallel paths in the stator. REs make rise loop currents which can be translated in the complex domain through a Fortescue´s space-transformation. Extensive simulations show that mainly 2(p±1)-pole current space vectors are stimulated by REs in 2p-pole SMs, with typical cardioid-shaped patterns. The simulation results were justified by using multi-phase symmetrical components, and theoretical formulas were obtained for fault severity assessment starting from loci amplitudes. Experimental verification was shown in a companion paper, where a Labview virtual instrument detects natural and artificial REs in a 17kVA four-pole generator.