Suppression of the inrush current of three-phase power transformers by controlled switching-on

Uncontrolled switching-on of power transformers leads to inrush currents with large magnitudes and small damping coefficients. One possibility to suppress that effect is given by controlling the switching moment for each winding with taking into account the load and remanence condition. The paper gives switching rules to manage the so called ''sequential switching'' of each phase of three-and five-leg-tranformers. Measurements on a three-leg-transformer with Y- and with Yn-connected primary windings verify the switching rules.