Core Loss in Fe-Si Powder Cores

Abstract

The applications of powder cores to very high power conversion equipment have recently been spreading. Fe-Si alloys are effective in downsizing magnetic cores because they have large degrees of magnetization. However, core loss needs to be further reduced. The relationships between core losses for Fe-3mass%Si powder cores made under various conditions were investigated in this study, i.e., hysteresis losses, classical eddy current losses, and anomalous eddy current losses including the sizes of their particles and crystal grains. We found that hysteresis losses decreased as crystal grains increased in size. We confirmed that not only there were classical eddy current losses generated uniformly in particles, but also anomalous eddy current losses occurred. The anomalous eddy current losses suggested that they were due to domain wall movement, and they decreased with decreasing crystal grain sizes. Their exponents of the frequency dependency of anomalous eddy current losses varied between 1.5 and 2.0 depending on test conditions, and they reflected the change in the number of domains with frequency.