Reignition Voltage of Arcs on Double-Break contacts

Experimental studies were made of the arc reignition voltage on double-break contacts for fine silver (Ag 1000), AgNi 90/10, AgCdO 90/10, and AgSnO
2
88/12. The experiments were carried out in an ac circuit with air-core reactors (power factor 0.4). The frequency of the transient recovery voltage oscillation ranged from 10 (or 5) to about 70 kHz. The reignition voltage after an arc having a duration of close to onehalf cycle (-~10 ms) was measured 15-25 times in a fixed-circuit condition. In the high-frequency range of the voltage oscillation, the value of the average reignition voltage does not depend upon the frequency, and at 103 A this constant value (immediate recovery voltage) is smaller than that at 57 A. The ratio of the reignition voltage (
\mu
Rd
) of the double break to that (
\mu
Rs
) of the single break at the same reignition time (time after current zero) has the value of 1.7-1.8 for AgNi 90/10, AgCdO 90/10, and AgSnO
2
88/12. Onlyfor Ag is the ratio (
\mu
Rd
/
\mu
Rs
) found, interestingly, to be almost two. This fact is considered to be due to the glow discharge which precedes the arc establishment.