End winding deformations in different turbo generators during 3-phase short circuit and full load operation

摘要

The measurement and calculation of end winding deformations for different turbo generators is presented. The measurements have been realized on three turbo generators of ratings from 94 MVA to 550 MVA. They have been done both for full load operation and for a three phase short circuit and were compared with calculation results. The nonlinearity and the influence of temperature on amplitudes and frequencies of the deformations is investigated. The calculation uses the method of Biot Savart to calculate the forces on the end winding section. The stator currents are calculated using Parks equation system and Finite-Difference-Calculations and have been verified by measurements. A 3-dimensional Finite-Element mechanical model of the end winding section is created, which considers not only the damping effect and the stiffness of the copper bars, but also of the bandages, brackets and isolation. The copper bars are modeled in the shape of evolutes. The construction of bandages, end rings and brackets has been varied. End winding eigenmodes and frequencies are given for these different design concepts. The results of measurement and calculation have lead to a deeper understanding of end winding behaviour and have been used for a new generator end winding design. This new design has been realized and tested on a 94 MVA turbo generator.