Analysis On Mechanical And Electrical Characteristics Of Generator Under Air-Gap Eccentricity And Winding Short Circuit Composite Faults

Taking the combined faults composed of the static air-gap eccentricity, the dynamic air-gap eccentricity, the mixed air-gap eccentricity and the winding interturn short circuit in the turbo-generator as the study object, this thesis analyzes the radial vibration characteristics of the stator&rotor, and the circulating current characteristics inside the parallel branch loop respectively under the normal condition, the air-gap eccentricity fault, the rotor interturn short circuit fault, the staor interturn short circuit fault, the air-gap eccentricity&rotor short circuit composite fault, and the air-gap eccentricity&stator short circuit composite fault. The main achievements obtained in the thesis can be drawn up as follows.(1) The formulas of the magnetic pull per unit area that causes radial vibrations to the stator, the unbalanced magnetic pull (UMP) in the horizontal direction and the vertical direction which brings in radial vibrations to the rotor, and the electromotive force (E.M.F.) difference between the two branches which produces circulatign currents inside the parallel branch loop are deduced. Since these formulas contain the main faulty parameters and express the fuction relation between these parameters and the magnetic pulls&E.M.F. difference, they can be provided as the qualitative analysis basis of the stator&rotor vibration and the circulating current characters. Also, these formulas can be used as the quantitative calculation reference of the magnetic pull and the E.M.F. difference.(2) The analysis and experiment verification on the stator&rotor radial vibration characters and the circulating current characters respectively under the refered six conditions are presented. The result shows that the mechanical and electrical faultly characters of the composite faults are greatly different with that of the normal condition and the single faults. Moreover, these characters can not be obtained through the simple character superposition of the composed fault types. The proposed analysis results will improve the failure criterion of the turbo-generator and offer a theory reference for the diagnosis of the air-gap eccentricity&winding short circuit composite faults.(3) The mapping relation between the air-gap eccentricity type and some specific components of the stator&rotor vibration and the circulating current, which can be provided as the reference for the composite fault diagnosis and will be beneficial to the fast identification of the eccentricity types, is obtained.(4) The upper bound amplitude expressions and the influential factors of the magnetic pull and the E.M.F. difference under the air-gap eccentricity&winding short circuit composite faults are obtained. Furthermore, the respective effect of the static air-gap eccentricity development, the dynamic air-gap eccentricity development, the rotor short circuit development, the stator short circuit development, and the exciting current increment on the stator&rotor vibration and the circulating current is investigated, based on which the faulty components'development monitoring can be carried out.