The voltage across the welding arc. See STANDARD WELDING TERMS.
Arc voltage is the total voltage between the electrode holder and the base metal immediately adjacent to the arc terminals. It is the summation of the cathode voltage drop, the anode voltage drop and the arc stream voltage drop.
Arc voltage may vary with a number of conditions, such as length of the arc, temperature, and gaseous content of the arc. Usually, as long as the welding current remains constant, arc voltage increases as the arc is lengthened and decreases as the arc is shortened.
This change in voltage, however, is not in direct proportion to the length of the arc. The voltage across a given arc length may also vary with current changes, because of the peculiar characteristics of the arc in which resistance decreases as current passing through it is increased.
When the arc torch uses two electrodes, the welding arc voltage is the total voltage between the two electrode holders.