Frequency dependence of the ferrite-loss increase caused by premagnetization

Ferrite cores of magnetic components used in power electronics are often biased with a DC or low frequency premagnetization. Work has shown that a bias field may have significant influence on the remagnetization losses and therefore has to be considered in the component design. Using a precise measurement setup this paper investigates the frequency dependence of the power loss increase due to premagnetization. The measurements are performed on typical ferrites of two major manufacturers. The experimental results show that there are two major contributions to the total remagnetization losses of soft-ferrites whereas only one contribution is influenced by premagnetization. Finally the paper discusses some aspects of a mathematical description for the bias problem and leads to an improved understanding that might be useful for the designer of magnetic components