Influence of the stacking method on the iron losses in power transformer cores

It has been hypothesized that different stacking patterns of grain-oriented silicon steel laminations cut at small angles to the rolling direction can reduce the iron core losses in power transformer cores. Experiments testing this theory are reported. The tests show that the hysteresis loss may be decreased when compared to the stacking in a standard core; however, eddy current losses are increased. The total iron losses do not appear to be reduced by cutting laminations at small angles to the rolling direction. However, for a few crosswise laminations, losses were not increased either. In these samples, hysteresis losses were decreased while reaching saturation at a lower level of magnetization. The eddy currents in these packets are increased due to the harmonics generated by the saturation. The net result is an increase of the overall loss value as the angle to the rolling direction increases. Changing the stacking pattern may be used to reduce harmonics without affecting the losses. This may contribute to the reliability of measuring transformers under extreme conditions