Arc Current:

As a general statement, arc current controls the weld penetration, the influence being directly proportional, if somewhat not exponential. Arc current also influenced the voltage, with the voltage at a fixed arc length enhancing in proportion to the current. For this purpose, to keep a fixed arc length, it is essential to change the voltage setting while the current is adjusted.

The procedure can be utilized with either direct or alternating current, the choice largely depending on the metal to be welded. Direct current along the electrode negative offers the advantages of deep penetration and quick welding speeds, especially while helium is used as the shield. Helium is the gas of choice for mechanised welding.

A third power option also is available, that of utilizing direct current with the electrode positive. This polarity is utilized only rarely because it causes electrode overheating. These effects of polarity are described in more detail in a following discussion of Direct Current.