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Xin Peng,Ge Baojun,Tao Dajun,Lv Pin 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.4
To research the variation characteristics and infl uence factors of air gap magnetic fi eld and electromagnetic torque of nuclear power half-speed turbine generator with stator winding inter-turn short circuit, the two-dimensional transient electromagnetic fi eld of generator-external circuit-grid coupling mathematical model is established by fi eld-circuit-network coupling method. Taking the national laboratory’s generator as an example, and comparing the simulation results of the inter-turn short circuit of the armature winding with experimental data, the correctness of the model is validated. On this basis, the simulation model of a 1407MVA nuclear power half-speed turbine generator is built. Then the stator winding inter-turn short circuit fault is simulated when the generator is connected to the grid with rated load. The characteristics of air gap fl ux density and electromagnetic torque are obtained before and after fault, as well as, the relationship between their each component and the fault degree is obtained. At the same time, the variation law of air gap fl ux density and electromagnetic torque is obtained when the relative position between fault winding and magnetic pole changes. The theoretical reference for fault diagnosis and localization using harmonic electromagnetic torque after fault is provided
Hu Zhiqing,Li Jiaji,Yu Ge,Lin Baojun 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.8
Clustering balls spinning method is a new method for fabricating curved surfaces by clustering rigid balls. It is always one of options to explore forming mechanism by using numerical simulation method that is closer to the real experimental process. In this article, we have adopted a new numerical model with multi-layer rigid balls (MlRB), which is named as MlRB model and more responsive to actual experiments. The model subroutine is developed based on the ABAQUS software. Simulation procedure using MlRB model is introduced, and cross-section, thickness distribution and springback using MlRB model are analyzed and compared to the experimental results and simulated results using previous numerical model with single-layer rigid balls (SlRB), which is named as SlRB model. The results are shown that, curved surface and thickness distribution simulated by MlRB model are closed to experimental results, and springback of curved surface is much less. Furthermore, auxiliary forming region that benefits to make the sheet deformed furtherly is proposed and analyzed. It is indicated that MlRB model is successful to simulate the deformation of the sheet according to the experiment, and it lays the foundation for the optimization of the technology parameters in the future.