A constant current (CC) arc welding power source is designed to hold output current within a narrow band as arc voltage swings with electrode-to-work distance, while a constant voltage (CV) source holds output voltage within a narrow band as current swings with wire burn-off rate [S1][S4]. TWI's static-arc data shows that, at a 150 A setting on a drooping CC machine, a ±5 V change in arc voltage produces roughly a ±8 A change in welding current, the steepness of the droop curve being the design knob [S4].
The dividing line between the two architectures is the static output curve, not the process label: SMAW (stick), GTAW (TIG) and mechanised submerged arc use CC (drooping) characteristics, while GMAW (MIG/MAG) and FCAW use CV (flat) characteristics matched to a constant wire-feed rate [S4]. Reference notes from NPTEL make the second-order point that "constant voltage" machines do not output a perfectly flat curve either, but a slightly downward-sloping one, a subtlety that matters when sizing a CV supply for pulsed or low-energy transfer modes [S7]. For background on the underlying energy delivery see the arc welder reference, and for the consumable-side tools that pair with these supplies see welding cutting tool.
Static output curve: drooping CC vs flat CV
The CC output is called a "drooping" or constant-current static characteristic: open-circuit voltage is highest, and once the arc strikes, voltage collapses while current rises along a steep curve [S4]. The CV output is called a "flat" or constant-voltage characteristic, holding volts nearly constant as the load draws varying current, again with a slight negative slope in real machines [S7]. On most modern inverter-class power sources, the slope of the curve is user-selectable, so a single box can be flattened for MIG or steepened for stick by changing a control setting rather than swapping hardware [S4].
For SMAW and GTAW, where the operator physically holds the torch or electrode holder, arc length is changing continuously, and the CC characteristic keeps current (and therefore penetration and electrode melt-off rate) within a narrow band even as the operator's hand moves [S1][S4]. Current, not voltage, sets the electrode consumption rate in pounds per hour or kilograms per hour, so locking current decouples metal deposition from the welder's tremor [S1]. The welding-cut toolchain that delivers this stable current is detailed in welding cutting tool, and the arc welder entry covers the closed-loop regulation that produces it.
Process pairing: SMAW/GTAW on CC, MIG/MAG/FCAW on CV
CC is the standard match for manual or semi-automatic processes with a non-consumable or stick electrode: SMAW, GTAW, and the mechanised submerged-arc (SAW) variant where an external arc-voltage feedback loop drives wire feed speed [S4]. TWI notes that SAW uses a drooping characteristic supply too, because the burn-off rate of the wire must be matched to a fixed current, with the wire feeder acting as the regulating element rather than the power source itself [S4].
CV is the standard match for GMAW and FCAW, both of which feed a continuous consumable wire at a fixed rate, so the power source's job is to hold voltage constant and let current fluctuate up or down as the arc gap self-adjusts [S4][S5]. The Fabricator's CV/CC primer (2014-05) summarises the same pairing rule: wire-feed processes get CV because the wire feeder is the loop that holds arc length, and stick/TIG get CC because the human welder is in the loop [S2]. This is also why portable wire feeders often carry a CV/CC switch: they let a multi-process inverter drive either a constant wire-feed MIG gun or a CC stick/TIG torch from the same output [S1].
Selection criteria: slope, open-circuit voltage, and process limits
Three numbers drive the CC/CV decision: slope of the static curve, open-circuit voltage (OCV), and the current range at rated duty cycle. On a CC supply, a steeper slope means smaller current change for a given arc-length change, which is the more stable condition for overhead stick work and out-of-position TIG, while a flatter CC slope gives the welder more deposition control by allowing deliberate arc-length changes to swing current [S4]. Open-circuit voltage for CC stick machines is typically limited to about 80 V DC for operator safety under IEC 60974-1-style limits, and OCV on CV MIG machines is usually set between 15 V and 40 V depending on material thickness and transfer mode [S1][S4].
Duty cycle at rated current, expressed as a percentage over a 10-minute window, separates hobby-grade CC inverters from shop-floor units: a 200 A at 60% rating at 40 °C ambient is a common benchmark for industrial stick/TIG, and a 250 A at 100% rating is a common benchmark for CV MIG production cells [S1]. Multi-process inverters that carry both modes are now standard in fabrication shops, and the deciding factor is rarely "which is better" but "which mode do I lock the front panel to for the next 8 hours of production." For guidance on deciding between process families for a given shop, the arc welder reference consolidates the duty-cycle and OCV trade-offs.
Comparison: CC vs CV on six decision criteria
Stability under hand motion: CC keeps current within roughly ±8 A at 150 A for a ±5 V arc change, giving stable penetration for hand-held stick/TIG [S4]. Self-regulation: CV relies on constant wire-feed speed and the burn-off rate to hold arc length, so human torch-height error is corrected automatically by the wire feeder, not by the power source [S3][S5]. Electrode compatibility: CC is required for non-consumable tungsten (GTAW) and stick electrodes whose melt-off is set by current alone, while CV is used with continuous solid and cored wires (GMAW/FCAW) whose length is set by feed speed [S1][S4]. Heat input control: CC gives the operator direct control of deposition via arc-length manipulation on a flat-slope curve, while CV gives heat input mainly through wire-feed speed and contact-tip-to-work distance [S4]. Application fit: CC for repair, field stick, pipe TIG, and aerospace GTAW; CV for high-deposition MIG/MAG on steel and stainless, FCAW on structural steel, and short-circuit or pulsed-spray transfer automation [S2][S4].
Pulsed and waveform-control supplies: the modern third category
Lincoln Electric's own reference notes that pulse welding with waveform-control technology power sources breaks the strict CC/CV dichotomy: the supply monitors and switches both voltage and current at rates much faster than conventional CC or CV loops, producing a stable arc that is neither [S1]. The Fabricator's 2014 primer and Hobart's welder-forum discussion both describe the same effect: a constant wire feed combined with pulsed current lets the supply mimic CC behaviour for penetration and CV behaviour for arc length in alternating cycles, which is the basis for STT (Surface Tension Transfer), pulse-MIG and AC TIG waveforms [S2][S3].
For a 2026 specifier, the practical implication is that the binary CC-or-CV question is most relevant at the budget tier and in field-stick applications; at the production tier, a single multi-process inverter with firmware-selected CC, CV, and pulse modes is now the default procurement line item, and the procedure qualification (e.g. ASME Section IX or ISO 15614-1) is written around the chosen waveform rather than the supply's marketing label [S1][S2]. This same trend toward multi-mode capability in compact inverters parallels the way a single vision light source controller can switch between structured and diffuse modes for different inspection tasks.
Failure modes and common mis-specification
Using a CV machine for stick welding produces a current that spikes upward as the operator dips the electrode, often sticking the rod to the workpiece and tripping the overcurrent protection, because the CV source tries to hold its set voltage and lets current run away into the short [S1][S6]. Using a CC machine for MIG without a constant wire-feed produces the opposite failure: arc length drifts as the operator changes hand position, voltage swings, and the wire either stubs into the puddle or burns back to the tip [S3]. TWI also flags that SAW with a CV supply, rather than the conventional CC supply, removes the burn-off-rate match that the wire feeder's arc-voltage feedback loop depends on, leading to unstable wire feed and inconsistent deposition [S4].
Field-reported fixes on Hobart's Weld Talk forum consistently show that a MIG gun plugged into a CC stick machine is a "learn by burning" lesson: the arc either short-circuits or balloons because the supply will not budge voltage to track a self-regulating wire [S3]. The reverse case is less destructive but produces ugly beads: a CV MIG supply on stick gives a soft, spattery arc because the voltage is locked and current cannot rise enough to clean the oxide layer on cellulosic or low-hydrogen rods [S1][S6]. The fix in both directions is a multi-process inverter with a front-panel mode switch, or two physically separate machines on the shop floor [S1].
Sourcing and standards
Authoritative reference material on CC vs CV comes from the equipment OEMs (Lincoln Electric), the welding industry press (The Fabricator, 2014-05), the open TWI Global job-knowledge articles, and the NPTEL welding lecture series hosted by IIT [S1][S2][S4][S7]. The underlying safety and performance framework for both CC and CV arc welding power sources is IEC 60974-1, which sets the 80 V DC open-circuit limit for operator-reachable circuits and the insulation, heating, and mechanical test regime that every nameplate rating must survive [S1]. Procedure qualification for the welds made by these supplies is typically written under ASME Section IX or ISO 15614-1, which reference the power source only by mode (CC or CV) and by the range of parameters used on the PQR [S2].
For a 2026 procurement or training spec, the next node is a multi-process inverter rated for the heavier of the two required modes (typically CC stick/TIG for repair shops, CV MIG for production), with a published slope curve and an OCV that satisfies IEC 60974-1 for the operator environment. Two trackable signals to watch: (1) OEM datasheets are now required by several large fab-shop customers to publish both the CC and CV static curves on the same plot, and (2) the migration of stick and MIG procedure qualifications onto shared multi-process supplies is being audited more strictly, so a PQR tied to "Inverter X in CC mode" no longer transfers automatically to "Inverter Y in CV mode" without a new test [S1][S2][S4].
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