Correlation of the Radially Integrated Properties of Gas Blast Arc Discharges

Extensive experimental results for the properties of the arc thermal region and local electrical conductances have been reported in the literature for both peak current and current zero phases of orifice air flow arcs. The present paper is concerned with interpreting these results in terms of boundary layer integral analysis concepts. "Characteristic area" and "shape factor" values are presented for orifice flow arcs and methods of correlating these parameters for different arcing conditions are examined. The results show that within experimental accuracy unique relationships exist between various shape factors and correlation parameters, over a wide range of arcing conditions including the current zero period of an ac waveform. The resulting correlation curves, therefore, form the basis for predictive calculations of arc behavior under different gas blast conditions. Finally, an illustration is presented of the manner in which the shape factor correlations may be used for determining the relative importance of various fundamental processes during the current zero period of a gas blast circuit breaker arc.