Experimental Evaluation of the Relationship between Filter Inductor Impedances and Dimensional Resonances of MnZn Ferrites

This paper explores the relationship between filter inductor impedance and dimensional resonance in magnetic cores. Experimental results were obtained showing multiple factors behind the resonances that appear in the frequency characteristics of inductor impedances: the inherent characteristics of a magnetic material, the self-inductance of an inductor and stray capacitance in its winding, and the winding acting as a distributed constant line. Next, based on the measurement results, the dimensional dependencies of the complex permeabilities (dimensional resonance) and the influence of dimensional resonance on inductor impedance are discussed in detail. Finally, this paper shows that the effect of dimensional resonance on complex permeability can be mitigated and filter inductor impedance can be increased in the high frequency range by a core lamination. These results are verified by the experiments described in this paper.