Arc duration of breaking arcs is investigated in order to obtain an experimental equation for the dependence of the arc duration on supply voltage in DC resistive circuit in air at atmospheric pressure. Materials of the contact pairs are Au, Ag, Cu, Ni, Pt and Pd. The interrupted current is ranging from 6 A to 10 A and the supply voltage is 30 V, 42 V and 54 V. Sato's experimental equation for the arc length is modified to obtain more appropriate experimental equation for our experimental results. The arc termination current It and minimum arc voltage Vm that are obtained with the experimental results are used as parameters of the experimental equation for each contact material. And characteristic coefficients C for each contact material in the experimental equation are obtained. As results, the experimental equation for each contact material well agrees with the experimental results. The experimental equation for several contact materials is presented.

An experimental equation of V-I characteristics of breaking arc was investigated in the air at atmospheric pressure. Material of the contact pair is Ag, Au, Cu and Ni. Supply voltage is set to 42, 48 and 54 V. The electrical resistance of experimental circuit is 5 Ω. The time evolutions of arc voltage, arc current and gap length were measured, simultaneously. V-I characteristics were obtained from those measured values. The dependence of the arc voltage on the gap length was represented by an approximate formula as a straight line in order to obtain the experimental equation. And the dependence of the strength of electric field of arc column on the supply voltage was approximated to a straight line. Using these approximate formulae, the experimental equation of the dependence of the arc voltage on the arc current was obtained with the gap length as a parameter. It was shown that the experimental equation agreed with experimental data in the experimental conditions for each contact material.