Flavio Calvano

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 and forces in the end winding regions of large turbine generators is presented. The proposed approach is based on an integral formulation for nonlinear magnetostatic problems. Its main advantage is the reduction of the discretization to only the 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 is presented. The analysis is based on a time stepping simulation where the currents are derived from the integration of a lumped parameter model.

Electromechanical analysis of end windings in turbo generators

Purpose – The purpose of this paper is to present a numerical approach for the computation of 3D magnetic fields in rotating electrical machines. The technique is suitable for the computation of flux densities and forces in the end windings of large synchronous turbo generators (TG).Design/methodology/approach – The magnetostatic FEM model of the generator end windings is carried out for different displacements of the rotor axis to the stator magnetomotive force (MMF) axis. The method is based on a parallel integral formulation allowing to substantially reduce the computational effort.Findings – The computational model requires only the discretization of magnetic materials and conductors and is fast enough for carrying out 3D analyses on a time scale fast enough for the needs of the designer. As far as the present application is concerned, the analysis of a synchronous generator in the class of 300‐400 MVA has shown that the most stressed elements of the armature conductors are those closer to the stator ...

Size Is in the Eye of the Beholder: Technique for Nondestructive Detection of Parameterized Defects

The paper presents a technique to compute magneto-quasi-static nondestructive testing problems with parameterized frequency and defect geometry. A single mesh is used for computations within a range of parameters, and the metric variations due to parameter variations are taken into account in the numerical values of the material parameters.

Computation of end-winding inductances of rotating electrical machinery through three-dimensional magnetostatic integral FEM formulation

Purpose – The paper aims to illustrate a numerical technique to calculate fields and inductances of rotating electrical machines. Design/methodology/approach – The technique is based on an integral formulation of the nonlinear magnetostatic model in terms of the unknown magnetization. The solution is obtained by means of a Picard-Banach iteration whose convergence can be theoretically proved. Findings – The proposed method has been used to build a model of a large turbine generator. In particular, the influence of end effects on flux linkages has been computed. It has been demonstrated that the 2D solution underestimates the flux linkages as well as the no load voltage of 2 per cent, while the leakage fluxes are computed by the 2D solution with errors as high as 20 per cent. Originality/value – The method is advantageous in comparison to standard methods.

Non-Iterative Imaging Method for Electrical Resistance Tomography

Electrical Resistance Tomography (ERT) is a body of methods and techniques aimed to reconstruct the spatial distribution of the resistivity of a material starting from the knowledge of boundary measurements such as, for instance, the Neumann-to-Dirichlet map. This inverse problem is ill-posed and nonlinear and, therefore, its solution require a considerable computational effort. In this paper we discuss a fast non-iterative reconstruction method for locating inclusions in an otherwise homogeneous material. This method, potentially, is a candidate for near real-time applications.