Rotor Vibration Difference Among the Single and the Combined Faults Composed by Static Air-Gap Eccentricity and Rotor Interturn Short Circuit

This paper investigates the rotor vibration differences among the rotor interturn short circuit fault, the static air-gap eccentricity fault, and the combined fault composed by the former two. The UMP (unbalanced magnetic pull) formulas of the three faults are firstly deduced. Then the rotor vibration characters, as well as the vibration difference comparison, are studied based on the formulas. Finally, the numerical calculation and the experiment of a non-salient fault simulating generator are taken to verify the theoretical analysis. It is shown that the rotor interturn short circuit fault mainly causes the rotor to vibrate at f _r (the rotating frequency of the rotor), while the static air-gap eccentricity fault primarily produces vibrations at 2f _r , and the combined fault generates vibrations at f _r , 2f _r , and 3f _r at the same time. The proposed work is available for the accuracy improvement of the generator fault diagnosis.