Magnetostriction in grain-oriented electrical steels under AC magnetisation at angles to the rolling direction

Magnetostriction is an important source of vibration and acoustic noise in electromagnetic cores. This study reports magnetostriction components along the rolling, transverse and magnetisation directions (MDs) of grain-oriented (GO) electrical steels, used for transformer and large rotating machine cores, under magnetisation at angles to the rolling direction (RD). Magnetostriction components in the sheet plane were simultaneously measured using a two-dimensional magnetisation system. Results from the measurements agreed with the magnetostriction calculated from a simplified model of magnetic domain patterns in a 3% SiFe single crystal. It is shown that the magnetostrictive strain along the RD is always the highest component in the sheet plane irrespective of MD. This is expected to cause both additional vibration at the corners of transformer cores where flux deviates from the RD and high radial vibration in the back-iron regions of rotating machine stator cores assembled from segmented GO steel laminations.