Arc recovery strength measurements

A SYSTEM has been developed for determining the recovery strength of arcs by means of a sine-wave source of current and a high-voltage pulse. Arcs can be studied at currents up to 8,000 amperes, and recovery voltages to 37 kv. The system is shown schematically in Fig. 1. In this figure, the 60-cycle arc-current circuit is designated by the heavy line. The arc under study is drawn in Switch I. The high-voltage pulse that is used to “probe” the residual plasma of the arc is applied between Switch I and Switch II. Switch II is used to isolate the high-voltage pulse from the low-voltage power source. The sequence of operation of the two switches is shown by the simulated current oscillogram of trace A of Fig. 2. Since Switch II is opened near the zero of the current wave, it is deionized much more rapidly than the switch under test and is therefore able to withstand much more voltage than that at which Switch I re-ignites.