Arc current, voltage, and resistance in a high energy, gas-filled spark gap

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Texas Tech University

A spark gap was designed and constructed to measure the time dependent arc resistance. The arc current was measured and the arc resistance calculated using the current and the other circuit parameters. Typical operating parameters were: unipolar pulse, 35 kV breakdown voltage, 30 kA peak current, and 1.15 kJ total energy per shot. The dissipated arc energy was calculated from the arc current and resistance and found to be between 4.5% and 10.5% of the total energy. Arc resistance vs time curves were obtained for all possible combinations of three electrode materials (304 Stainless Steel, ACF-IOQ Graphite, and 3w3 Copper-Tungsten), three gases (Air, N2, and SF6), and three gas pressures ( 1 , 2, and 3 atmospheres). Statistical analysis was performed on the resultant data. Essential results are: within the statistical and measurement errors, the resistance is independent of the electrode material. For each gas, R is approximately proportional to pd (pressure and gap distance). The constants of proportionality are (31 ± 7) mΩ/(cm bar) for air, (47 + 15) mΩ/(cm bar) for N2, and (76 ± 17) mΩ/(cm bar) for SF6.

Breakdown voltage, Electric arc, Electric discharges through gases, Pulse circuits