Characteristics Analysis of the Square Laminated Core under DC-biased Magnetization by the Fixed-point Harmonic-balanced FEM

Abstract

The ferromagnetic core of power transformer is susceptible to DC bias and has special nonlinear and hysteretic characteristics under DC-biased magnetization. The DC bias test is carried out to obtain the DC-biasing magnetization curve of a square laminated core (SLC). The harmonic-balanced finite element method (HBFEM) is combined with the fixed-point technique to calculate the magnetic field in the laminated core under DC bias conditions by means of the measured DC-biasing magnetization curve. A locally convergent method in harmonic domain is presented to determine the fixed-point reluctivity, which can speed up the convergence of harmonic solution. Computation of DC-biasing magnetic field in SLC is performed by means of normal and DC-biasing magnetization curves respectively. Comparison between computed and calculated results indicates DC-biasing magnetization curve should be adopted in calculation of magnetic field under DC-biased magnetization.