Analysis of Magnetization Curve Approximations for Nonlinear Calculation of an Eddy-Current Field

Simulation of the eddy-current fields in the ferromagnetic materials is impossible without information on the dependence of the magnetic field induction on its intensity—the magnetic curve. Experimental determination of the magnetization curves encounters technical problems and the reference data contain, as a rule, a small number of values and they are unsuitable for direct application. For this reason, the transition from original magnetization curve to its approximation is relevant. Three very popular approximation methods of the magnetization curves in the calculation practice are considered in this article: the Frelich approximation, the Melgui approximation, and the universal Pentegov approximation. The average deviation from the original magnetization curve, difference in the average density and the calculation error of the active power are accepted as the approximation effectiveness. The experimental data about magnetization of materials with different properties were used for comparative analysis of approximations. It is shown that the minimum error in calculation of eddy-current fields is provided by the universal approximation. Replacement of the magnetization curve by other approximations may lead to calculation errors of active power exceeding 15%. The obtained results may be used for the nonlinear finite element analysis of the eddy-current field in ferromagnetic materials.