Interruption of Low-Voltage DC Arc in Air under Axial Magnetic Field

This paper represents the findings from our research in which a series of experiments were conducted on dc current interruption in air in axial magnetic field provided from rare earth magnets mounted in the test electrodes. The experimental range was as follows: Arc voltage 80-100 V, arc length 5-10 mm, arc current 80-800 A, and applied field 35-2400 G. The free-burning arc diameter was measured in these experiments from high-speed photographs. It was found that a strong magnetic field can improve the interruption capacity of air-arc significantly. In the experiments, the successful switching time of both 220 and 330 A free-burning air-arc in 2.4 kG was less than half of the successful switching time of corresponding free-burning arcs in air. For higher current arcs, the outcome was more encouraging. An 800 A free-burning arc sustained for about 48 ms, whereas a 315 G field interrupted it within 8 ms. The information found on arc-root diameter and current density of 80-800 A free-burning arcs in air has filled a gap of data found in the literature. This information, in turn, will help to improve the theories available on free-burning arcs.