Thermal Interruption Performance of Ultrahigh-Pressure Free-Burning Nitrogen Arc

In this paper, an experimental investigation of the thermal interruption performance of free-burning nitrogen arcs at 1 bar, 20 bar, and 40 bar filling pressures is reported. This work contributes to the fundamental understanding of arc characteristics at very high gas filling pressures. A resonant circuit is used to generate an arc peak current of 130 A at a frequency of 190 Hz. An ignition copper wire initiates the arc between a 4 mm diameter pin electrode and a ring electrode. The arc burns freely at a fixed inter-electrode gap of 50 mm without any forced gas flow. A resistive-capacitive branch parallel to the arc controls the initial rate of rise of recovery voltage. By changing the parallel resistance, the rate of rise of recovery voltage is varied from 9.8 V/µs to 84.8 V/µs. Time to re-ignition and the corresponding re-ignition voltages are considered as the primary parameters to characterize the thermal interruption performance. It is observed that the re-ignition time rises with the decrease of rate of rise of recovery voltage at all pressure levels, which is expected. However, in the absence of a forced gas flow, high gas filling pressure results in a reduction of the time to re-ignition and the re-ignition voltage in contrast to atmospheric pressure nitrogen arc.