AN ITERATIVE FINITE ELEMENT - BOUNDARY ELEMENT METHOD FOR EFFICIENT MAGNETIC FIELD COMPUTATION IN TRANSFORMERS

The paper proposes a new procedure for magnetic field computation in multiply connected ferromagnetic domains. The magnetic field in ferromagnetic bodies is computed using the Finite Element Method (FEM) with Dirichlet boundary conditions and the vector potential normal derivative is obtained. This becomes the boundary condition for the Boundary Element Method (BEM) applied in free space, from which the new value of the vector potential results. The relative high permeability of the ferromagnetic bodies insures the convergence of the procedure. The nonlinearity of the ferromagnetic bodies is treated using the polarization fixed point method (PFPM), in which the polarization is corrected in terms of magnetic field strength H, in order to have a high permeability. The method was applied for the magnetic field computation in a transformer.