Building factors of transformer cores made from low loss Si-steel sheets

Grain-oriented silicon steels of various thickness were built into 3-phase stacked cores, and the relationship between the building factor (B.F.) and the material loss was discussed. The loss component proportional to square of frequency ( W e ), and the ratio of W e to total loss too, decrease as the thickness of the silicon steel decreases, while the loss component proportional to frequency ( W h ) is nearly constant for the high grade silicon steels of various thickness. In the case that silicon steels have same thickness, the B.F. deteriorates with decreasing material loss. But in the case that the thickness varies for high grade steels the B.F. does not change in spite of varying material loss. Using thin silicon steels, the core loss of transformers can be decreased in the same ratio of the material losses.