The geometry of arc interruption — II current-zero phenomena

THE final proof of the ability of an a-c circuit interrupter to sever the circuit, whether it be a circuit breaker, fuse, lightning arrester, or rectifier, is determined over the very short interval in the region of current zero. At each current zero in the arc or conducting medium the important thermal actions of the arcing or conducting period are integrated¹ and pitted against the recovery-voltage transient to determine the outcome, the success of which is termed interruption. The environment of the arc, not only the medium of interruption but the nature of the adjacent circuits,^2,3 plays an important role in the phenomena of circuit interruption. The arcing period, in particular, is capable of having a tremendous influence upon the current-zero phenomena.¹ In addition, however, the circuit interrupter is capable of imparting changes in the normal current flow in the region of current zero which play an important part in the final outcome.