Representation of high saturated ferromagnetic materials in the finite element analysis of power transformers

In most applications, eddy current losses in ferromagnetic material are generated in a rather thin layer immediately at the surface. The thickness of the saturated layer is limited to a few millimeters, otherwise the losses would cause excessive heat. A novel material formulation with some simplifications regarding the nonlinear magnetic characteristic within the finite element analyses represents the actual behaviour quite accurate. The utilized surface elements deal with the fundamental harmonic of flux density and current density, respectively. Thus, it is possible to represent the mutual influence of flux and eddy currents for complex geometries including ferromagnetic material in a very eflicient way.