Analysis of stator winding parallel-connected branches circulating current and its application in generator fault diagnosis

Through calculating the generator parameters of air-gap magnetomotive force, magnetic permeability, magnetic flux density, stator winding parallel-connected branches electromotive force distribution, the characteristics of the stator winding parallel-connected branches circulating current are analyzed. The results discover that the, second harmonics circulating current will increase when the rotor winding inter-turn short circuit fault occurs, and the fundamental circulating current will increase when the stator winding inter-turn short circuit fault or the air-gap eccentricity fault occurs, neither being strongly affected by the imbalance fault. Considering the differences of the circulating current characteristics caused by different generator faults, a method of generator fault diagnosis, based on the stator winding parallel-connected branches circulating current characteristics, is developed. Finally, the circulating current of a type SDF-9 generator is measured in the laboratory to verify the theoretical analysis presented above.