While energizing large transformers, so called inrush magnetizing currents lasting up to several tens seconds, the peak value of which are several thousand amperes in maximum, are observed. Due to the magnetic saturation phenomena in the iron core and the residual initial flux, and according to the principle that the value of the flux change in the saturated region corresponds to the constant applied voltage, such high value of currents flow. Fig. 1.3 shows an extreme case with maximum residual flux. The currents decay to the ordinal magnetizing value of less than several amperes by the losses in the circuits. The analysis is, due to the non-linearity, difficult, so digital calculations are recommended. A typical example (EMTP data and a result) is attached.
