Resistivity and core size dependencies of eddy current loss for Fe-Si compressed cores

In this study, resistivity and core size dependencies of eddy current loss were investigated for Fe-Si compressed powder cores. Over the resistivity of about 0.01 Ωm eddy current loss is independent on core height, however when the resistivity is lower than about 0.01 Ωm it increases with decrease of the resistivity. And eddy current loss increases as the core height is high. It is supposed that over about 0.01 Ωm eddy current generates only inside each particle, so eddy current loss does not depend on the core height, while under about 0.01 Ωm as eddy current flows through particles, eddy current loss depends largely on core height. Furthermore eddy current loss is proportional to the 1.70th-1.95th power of frequency, and the exponent changes with resistivity. It is suggested that under the situation of intra-particle eddy current, domain wall motions relate to the eddy current loss.