Effect of Dimensions on Power Losses in Mn-Zn Ferrite Cores

Two types of Mn-Zn ferrite cores¿high-permeability samples with low hysteresis losses, and converter materials with good high-frequency characteristics but large hysteresis losses¿were immersed in acid to gradually reduce their external dimensions, and the resulting change in large-amplitude losses and small-signal characteristics was measured. The core loss per cycle was lowered with reduction in dimensions for the high-permeability samples, but not for the converter materials; and the hysteresis loss increased for very small high-permeability core sizes, while that of the converter materials remained constant. These differences are explained in terms of the different microstructures and domain structures in the materials.