Grain Size Effects in Silicon Steels upon the ac Core Loss Components

Abstract

For some time it has been recognized that the sum of the classical eddy-current core loss and the loss represented by the dc hysteresis loop does not equal the total core loss. This error has been referred to as the anomalous or unaccounted loss. In recent years attempts have been made to account for this anomalous loss by utilizing modern domain concepts. It has been postulated that at small ratios of domain size to sheet thickness the anomalous loss should go to zero. Likewise at large ratios of domain size to sheet thickness, the eddy-current loss could be several times that predicted by the classical equation. In an attempt to explore the effects of grain size upon core loss components, it was found that the anomalous loss was nearly independent of grain size at constant thickness. If it is assumed that the magnetic domain size increases with increasing grain size, these measurements refute the importance of the changing domain size in the modern domain eddy current theories. However, it was noted that the dc hysteresis loss portion of total core loss changes significantly with grain size.