Single-wire machines commonly run from around 650 up to 1200 or 1500 amps, and multi-wire installations multiply that across several sources. Because seams are long and continuous, the rating that matters is output at 100 per cent duty cycle, not a peak figure at a lower duty that the process would exceed within the first minute of a pass.

Constant voltage with a fixed-speed feeder is the common choice for solid wire up to moderate diameters, since burn-off self-regulates and setup is simpler. Constant current with a voltage-sensing feeder suits larger diameter wires and deep-penetration heavy plate work, where it gives better control of penetration and copes with the higher melting demand.

It controls arc blow. At the currents submerged arc uses, the arc's own magnetic field and any residual magnetism in the work deflect it enough to cause undercut, lack of fusion and erratic bead placement. AC substantially reduces that deflection, and in tandem and multi-wire systems it also limits magnetic interaction between adjacent arcs.

Adjustment of the proportion of time and current spent in each polarity. More electrode positive gives deeper penetration; more electrode negative raises deposition rate at lower penetration. On trail wires in a tandem system this is how fill rate is increased without digging into the base metal, and frequency adjustment stiffens or softens the arc.

Each wire needs its own source, sized for the current that wire will carry, and the set must be capable of synchronised operation so the arcs do not fight one another. Lead wires are typically DC for penetration and trail wires AC for fill, so the specification is usually a matched package from one manufacturer rather than assembled from separate machines.

Three-phase at industrial voltage, with cabling and protection sized for a continuous rather than intermittent load - a point often underestimated when a first submerged arc station is added to an existing shop. Confirm supply capacity, cable size and protective device rating against the machine's continuous input current, not its average consumption.

Modern units generally do, logging current, voltage, wire feed and travel speed against a weld identity. Because the arc is invisible, this record is the main real-time evidence that a pass ran to procedure, and on code work it becomes part of the documentation alongside non-destructive testing results.