Post-arc currents of vacuum interrupters with axial magnetic field contacts under high current and voltage stress

The post-arc current of vacuum interrupter units with bipolar axial magnetic field contacts has been investigated under conditions of high current (40 to 60 kA RMS) and high steepness of the transient recovery voltage (5 and 10 kV//spl mu/s). The arcing time and contact distance, respectively, has been changed by varying the moment of contact separation. By comparison with simulations, the measured clear decrease of the post-arc current and charge with decreasing arcing time can be attributed to lower residual ionization. The dependence of the post-arc current on du/dt is explained by the influence of secondary emission.