High Frequency Permeability Measurements and Modeling of Magnetic Powder Cores Under DC Bias

Powder cores are attractive magnetic components for high-current applications due to their high saturation flux densities, combined with good high-frequency performance and relatively low losses. Although considered in many applications, only little information about their high-frequency properties under DC current bias exists. Therefore, this work describes a novel measurement methodology to determine the complex permeability of magnetic powder cores under superimposed DC bias. A comparison against alternative approaches reveals the advantages of the proposed methodology with respect to maximum frequency and bias current. Different types of powder cores are characterized at frequencies between 10 kHz and 100 MHz and superimposed currents up to 2.5 kA. Moreover, a simple phenomenological model is outlined that captures the permeability spectrum under DC bias. The model can conveniently be translated into equivalent circuits for use in system-level simulations.