Coupled Three Dimensional Numerical Calculation of Forces and Stresses on the End Windings of Large Turbo Generators via integral formulation

A novel numerical approach to calculate the time evolution of the three dimensional distribution of the magnetic field in the end winding regions of large turbine generators is presented. The proposed approach is based on an integral formulation for non linear magnetostatic problems within the frame of the finite element analysis. The integral formulation compute the eddy current and the magnetization and, therefore, its main advantage is the reduction of the discretization only to the part of the domain made by conductors and magnetic materials. In this paper the solution of a coupled magnetostructural problem consisting in the calculation of the mechanical stresses and deformations caused by the electrodynamic forces during a short circuit transient is presented. The currents used in the magnetostatic model are derived from the integration of a lumped parameter model. A specific parallel implementation customized for the proposed application makes of practical application the proposed technique.