Core Material Characterization under DC Bias Conditions

This paper investigates the impact of a DC premagnetization on permittivity, conductivity, permeability, as well as core losses across various frequencies in the ferrite N87 (TDK). The aim is to better understand the reasons behind the increase in loss due to a DC premagnetization and to explore how dimensional effects, such as bulk eddy currents or dimensional resonance, are influenced by a DC magnetic field. Experimental results show that the application of a DC bias primarily influences magnetic core losses through modifying the material's complex permeability, while exhibiting no significant effect on its permittivity and conductivity. To account for the observed increase in core losses under DC bias conditions, we introduce a small-signal DC Bias Loss Factor, the "DC Permeability Loss Estimator" (DPLE). This factor can be extracted from simple measurements and can help predict core losses under DC Bias condition.