This article presents a comprehensive analysis on the end winding vibration characteristics due to different stator inter-turn short circuit (SISC) positions in synchronous generators. Different from other studies, this article not only pays attention to the effect of SISC on the end winding electromagnetic forces, but also considers the impact of the short circuit position, which is related to the static air-gap eccentricity, on the end winding vibrations at the meantime. The whole work is based on the qualitatively theoretical analysis, the finite element analysis (FEA), and the experimental validation on a 6-pole synchronous generator. The study shows that SISC will considerably enlarge the electromagnetic force and intensify the radial vibration of the end winding, especially at 100 Hz, 200 Hz and 300 Hz. The closer the short circuit position is to the minimum air-gap point, the more severe the end winding vibration will be.

This paper proposes a novel hybrid model for analyzing the electromechanical characteristics under stator interturn short circuit (SISC) fault in synchronous generators. The hybrid of the model lies in that it considers the static air-gap eccentricity (SAGE) and SISC at the same time. Different from other studies, the proposed model can manage not only the impact of the short circuit degree, but also the influence of the short circuit positions, on the magnetic flux density (MFD) which is the basis to analyze electromechanical characteristics. The phase current and the electromagnetic torque (EMT) are selected in this paper as the representative of the electrical parameter and the mechanical parameter, respectively. 2D finite element analysis (FEA) and experimental studies confirm the validation of the proposed model. The model employs two primary factors, i.e., the short circuit turn number $n_m$ and the position angle $\alpha_sm$ , to reflect the short circuit degree and the short circuit position, respectively. By feeding these two factors as well as the detailed parameters of the generator into the model, the electromechanical feature data such as the phase current and EMT can be quickly assessed, and the developing tendency of the key MFD-based parameters can be conveniently predicted.

This paper mainly focuses on the impact of inclined static air gap eccentricity (ISAGE) on the electromagnetic characteristics and mechanical performances (vibration, deformation, strain and stress). Considering different ISAGE fault types in the theoretical and finite element analysis (FEA) model of synchronous generators, the effects of intersection position of the rotor center axis and stator center axis, rotor inclined angle, and the combination of the previous two fault types on MFD, phase current and radial magnetic pulling per unit area (MPPUA) are analyzed and compared. Then, based on the stator model used uniformly in three physical fields, the harmonic response and mechanical response are investigated with loads imported by the electromagnetic field. Finally, the stator radial vibration measurement experiments are carried out to verify the results obtained by theoretical analysis and FEA. It is shown that ISAGE will considerably enlarge the fluctuation of MPPUA and intensify the radial vibration of the stator, especially at the 2nd harmonic. The probability of failure at tooth tip and inner slot wall of the stator will increase.

Besides the static stator interturn short circuit (SSISC), the dynamic stator interturn short circuit (DSISC) may also occur in synchronous generators. However, at present, there is no effective model which can effectively analyze the generator characteristics under DSISC and identify the fault. To address this issue, this paper creatively presents a novel analysis model of DSISC for the first time. The degree and the position of short circuit are taken into consideration. Besides, the rotor vibration characteristics are comprehensively analyzed and compared under DSISC and SSISC. Further, the finite element (FE) calculation and the experiments are carried out on the CS-5 prototype generator. Meanwhile, the rotor mechanical response caused by the unbalanced magnetic pull (UMP) is obtained. The validity of the proposed model is confirmed by FE calculation and experiments. This paper provides the theoretical support for the diagnosis of DSISC fault in synchronous generators.

This article has conducted a comprehensive study on the stator and rotor vibration characteristics of the doubly‐fed induction generator (DFIG) in the case of radial air gap eccentricity (RAGE). Differently from other previous studies, this paper not only investigates the vibration characteristics of stator and rotor in radial static air gap eccentricity (RSAGE) and radial dynamic air‐gap eccentricity (RDAGE) fault but also takes the radial hybrid air gap eccentricity (RHAGE) into account. Through theoretical derivation, the detailed expressions of stator magnetic pull per unit area (MPPUA) and rotor unbalanced magnetic pull (UMP) are obtained. The finite element analysis (FEA) and experiment based on a two pairs of poles DFIG, and the results are consistent with theoretical calculations. It is shown that RAGE will enlarge the magnitude of stator MPPUA/vibration and rotor UMP/vibration. Specifically, RSAGE will not change the frequency components of stator MPPUA/vibration but will bring new frequency components to rotor UMP/vibration. However, both stator MPPUA/vibration and rotor UMP/vibration will generate new frequency components during RDAGE fault. In addition, the effect of RHAGE is the superposition of RSAGE and RDAGE. The research conclusions obtained in this paper can be used as a supplementary criterion for diagnosing the eccentricity of DFIG.