Magnetically driven high current switching arcs in vacuum and low pressure gas

The behavior of high current switching arcs in transverse magnetic fields is essential for the design of switching elements, in which arc motion is used to reduce contact erosion. In this paper magnetically driven arcs in vacuum and low pressure gases are investigated at currents of several tens of kA. Arcs driven in a low pressure environment exhibit a peak arc velocity of more than 1/spl times/10/sup 5/ m/s, exceeding those of comparable vacuum arcs by at least two orders of magnitude. The influences of current amplitude, gas pressure, and the kind of gas filling on the arc velocity are investigated. A threshold behavior concerning the minimum requirements for a nonstationary arc is found. An improved model is presented, which explains the observed peak arc velocities in vacuum and in low pressure gases.