Negative Sequence Eddy Current Field Analysis and Temperature Calculations of 1100MW Turbo-generator with 3D Finite Element Methods

摘要

Generally speaking, there's negative current in the stator windings of turbo-generators when operating with unbalance currents. Then a negative direction rotating magnetic field with twice power frequency will be caused in the machine. It's important to limit the negative sequent current level and its duration. Therefore, detailed calculations or analysis of negative sequence eddy current field and temperature field is required, especially during the period of new type turbo-generator development. In this paper, a parametric 3D negative sequence eddy current field analysis model of 1100MW 4-pole turbogenerator is established. The 1100MW 4-pole turbogenerator is a new type turbo-generator using in nuclear power plants. The 3D negative sequence currents arising from unbalance system operations in large turbo-generators are studied by using the finite element method. And the physical theory base of negative sequence eddy current field analysis is Maxwell equations. The mathematical models of large capability 4-pole turbo-generators are proposed to predict the negative sequence eddy current and temperature fields. In order to emulate the distributed exciting sources of the negative sequence current fields with enough precisions, the geometrical complication of the stator are accurately modeled in the proposed solid models, making it be readily to take into account of practical distributions of the negative sequence exciting currents. The sequence eddy current fields analysis of large turbo-generators includes both steady state and transient state analysis. To obtain temperature calculation results, some solving techniques of coupled fields are introduced. The temperature field analysis of large turbogenerators also includes both steady state and transient state analysis. And finally, the eddy current, loss and temperature distributions of the 1100 MW generator operating with negative current are obtained, for both analysis states. The computational results are shown in 3D colored figures, thus it's easy to get an overview of the eddy current, loss and temperature distributions. The results of steady state and transient state negative sequence analysis are in accordance with the standard IEC 60034-3. This study provides a basis for the design and operation of large capability turbogenerator.