The effect of tensile stress on the power loss of 3% grain-oriented silicon-iron

The domain wall motion and localized power loss have been measured under applied tensile stress for individual grains in polycrystalline commercial grain-oriented silicon-iron. The variation of power loss with tension results show that the greatest reduction in loss occurs at the higher values of frequency and flux density, which is when a large degree of bowing occurs. This reduction in power loss is due to the changes in the extrapolated static hysteresis loss and the excess eddy current (anomalous) loss as the tensile stress is increased. The reduction in hysteresis loss is primarily due to the decrease in wall spacing, whereas the change in anomalous loss is dependent upon the combined change of wall profile and decrease in wall spacing. Certain grains were found to have 50% of power loss of grains of similar thickness, orientation and diameter and the reasons for this low loss are described. It is shown that the application of a tensile stress of 7 MPa causes the greatest decrease in power loss and a further increase in tensile stress only has a marginal effect on the power loss.