Abstract
This paper presents a comprehensive analysis on the transient electromagnetic force behavior of the stator windings in a QFSN-600-2YHG type turbo-generator. Different from other studies, this paper investigates not only the distribution regularities of the resultant force and the force density, but also the force harmonic characteristics, and the mechanical responses which will cause sensitive impact on the insulation wearing. The whole work is generally based on a proposed simplified model and the 3D finite element coupling calculation. The simplified model contains two parts. The first part is the theoretical model that employs the approximate solution of the image current to obtain the analytic formula of the electromagnetic force on the end windings conveniently. The second part is the FEA model that employs only the end windings and one-tenth of the stator core to save the calculating memory and, meanwhile, obtain the qualified electromagnetic force as well as the mechanical response. It is shown that the nose-top, the connection point between the line part and the end part, and the middle of the involute are the three most dangerous positions of the end winding to sustain serious insulation wearing. Moreover, the winding, which endures the maximum mechanical response, is neither always consistent with the one that has the largest resultant electromagnetic force nor directly in accordance with the winding that affords the most intensive electromagnetic force density. The findings in this paper will be beneficial for the insulation monitoring and the manufacturing improvement on the stator windings.
Highlights
Stator windings are key parts in the generator for energy transformation and electricity output
This paper presents a comprehensive analysis on the transient electromagnetic force behavior of the stator windings in a QFSN600-2YHG type turbo-generator
As the capacity of the generator becomes larger and larger, the electromagnetic forces acting on the stator windings, especially on the end regions, will be increased greatly [1]
Summary
Stator windings are key parts in the generator for energy transformation and electricity output. Number of series turns in each phase simulations on the electromagnetic force densities in the three-phase short circuit condition [10] and the leading power factor case [11] were carried out, respectively These studies mainly paid attention to the electromagnetic force itself, while the consequent responses such as the mechanical vibration deformations and strains, which will cause dynamic wearing to the winding insulation, have been rarely investigated in depth. In view of the difficulty of 3D numerical solution due to memory limit, many researchers manually loaded a relatively stable electromagnetic force value to the 3D FEA model to solve the mechanical response on the end windings This method can generally get the force distribution tendency, the result is not precise enough. The analysis includes the distribution regularities of the electromagnetic force, and the force harmonic characteristics, and the mechanical response properties including the von-misses stress, the total deformation (reflecting the vibration amplitude), and the von-misses strains
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