Investigation on stator vibration characteristics under air-gap eccentricity and rotor short circuit composite faults

This paper investigates the stator vibration characteristics of turbo-generator, respectively, under normal condition and the air-gap eccentricity and rotor interturn short circuit composite fault, with the effects of the eccentricity factor and the short circuit factor on the stator vibration characteristics presented. The air-gap magnetic flux density and the unit magnetic pull under the composite fault are firstly deduced. Then three kinds of eccentricities are, respectively, considered to analyze the stator vibration characteristics. Finally, experiments are taken on a SDF-9 non-salient fault-simulating generator to verify the theoretical results. The study shows that when the composite faults occur, the eccentric kind determines the vibration components. 1st to 4th harmonic vibrations will be produced when the eccentricity is the static one, while 1st to 6th harmonic vibrations will be produced when the eccentricity is the other two. The increment of the interturn short circuit will increase the 4th harmonic vibration, but decreases the 2nd harmonic for the static eccentricity situation, and increase the 6th harmonic vibration for the other two eccentricities. However, no matter which kind of eccentricity increases, each stator vibration component will be increased. The presented work has reference value and positive meaning for the diagnosis of composite faults.