Approximation of Hysteresis Loops of Transformer Steel Sheets

Lines of the magnetic field in corners and T-joint points of transformer cores are not parallel to the rolling direction of the transformer sheets. Similar cases can occur in certain parts of the transformer columns during overcurrent states because the leakage flux can reach significant values. The hysteresis loops for magnetization directions other than the rolling direction are significantly different from each other. The paper describes a method allowing approximation of the hysteresis loops for any direction of the axial magnetization and for any value of the field strength in the transformer cores. The calculation results are compared with the real hysteresis loops measured for a chosen transformer sheet.