Calculation of Self- and Mutual Inductances of Power Transformers Using a 3D Modified Magnetostatic Integral Equation Approach

This work presents a novel three-dimensional calculation of self- and mutual inductances of a power transformer, based on a 3D magnetostatic integral equations approach and point matching. Influence of a ferromagnetic core is modeled with a constant magnetization over an element. In order to avoid the well-known cancellation error in calculation of the magnetic field inside the closed ferromagnetic core of a transformer, an additional line integral equation of magnetic field in a closed path, which is explicitly enforced to match magnetomotive force, is appended to the procedure. Overdetermined system of linear equations is assembled by point matching and solved by the least squares method. Results of the calculation for high voltage windings of a power transformer are in good agreement with results obtained by commercial FEM package Ansys Maxwell.