Effect of multi-axial stress on iron losses of electrical steel sheets

The effect of multi-axial stress on the iron losses of a non-oriented electrical steel sheet under alternating magnetization is analyzed. Multi-axial magneto-mechanical measurements on a M400-50A grade non-oriented electrical steel sheet are performed by using a custom made single sheet tester device. The measured losses are separated into hysteresis, classical and excess loss components by using statistical loss theory, and the effect of various stress configurations on the hysteresis and the excess loss components is analyzed. By utilizing the statistical loss theory, an equivalent stress model and a magneto-elastic invariant based model are derived. These models can be used to predict the iron loss evolution under multi-axial stress even if only uniaxial stress dependent measurements are available. The accuracy of both models to predict the multi-axial stress dependent iron losses is found to be satisfactory when they are identified only from uniaxial stress dependent measurements. The invariant based model is shown to be slightly more accurate for the studied material.