Abstract
One of the main factors in the acoustic noise of power transformers is thought to be magnetostriction of the cores, because the magnetic flux deviates from the easy axes at the corners of the cores. Therefore, we measured the magnetostriction and observed the domain structure in single crystals of (100) Si-Fe sheets when the easy axes deviated from the exciting direction. Complicated behaviors involving shrinkage and expansion were observed in the measured magnetostriction. In the demagnetized state, 180° domain walls parallel to the [001] direction were observed. When a small field was applied, a [010] domain was generated at the edge of the sample. The [001] and the [010] domains are partitioned by a 90° domain wall, whose movement caused large shrinkage. In a larger field, rotation of the magnetization caused large expansion. Thus, it became clear that large vibrations with magnetostriction were generated at the corners of the core, even if the cube-textured Si-Fe was used as the core's material.
