Arc interruption phenomena in a magnetic field

ARC IMMOBILITY and arc reversal phenomena limit the use, affect the design, and dictate the test procedure required for aircraft circuit interrupting equipment using magnetic arc suppression. Laws of physics which earth-bound electrical designers use unquestioningly are found to require re-examination when applied to magnetic arc interruption equipment for use at altitude. It had been assumed for more than half a century that an electric arc, like any other conductor free to move in a magnetic field, would move in a direction determined by Ampere´s Law. This assumption is valid, for all practical purposes, for circuit breaking equipment operating at sea level. However, as the altitude is increased, an electric arc in a magnetic field may falter, stop, and finally reverse its direction of motion.