Abstract
In this paper, the impact of forced cooling on the dielectric recovery of ultrahigh pressure nitrogen arc is experimentally investigated. The dielectric recovery is studied by applying 10-kV high voltage pulse at different instances after current zero. The current amplitude and the half cycle duration are kept at 425 A and 540 µs respectively. To examine the pressure dependence on the dielectric recovery, three different pressure cases are investigated: 1, 20 and 40 bar. First, dielectric recovery of nitrogen arc is studied without forced cooling by adopting a free-burning arrangement at different filling pressures. Afterwards, a puffer arrangement is used to investigate the impact of forced cooling on dielectric recovery. When the puffer arrangement is used, the position of the puffer disc and the blowing pressure are recorded. It is found from the experiment that, the arc voltage before current zero rises because of enhanced cooling due to forced gas flow. Unlike free-burning arcs where the dielectric recovery just after current zero, i.e., the thermal phase, is found to deteriorate in case of higher filling pressures of 20 bar and 40 bar, the gas flow generated from puffer with high filling pressure significantly improves the recovery process even in the thermal phase.