Which voltage characteristic is commonly used for GMAW equipment?

• A. Constant current
• B. Pulsed current
• C. Alternating current
• D. Constant voltage

Answer: (D)

In GMAW, the power supply is normally constant voltage. Keeping the arc voltage roughly fixed over a wide range of conditions lets the current adjust automatically with changes in wire feed speed and arc length, which helps maintain a stable arc and consistent heat input. Because the voltage stays steady, the operator can control the process by varying the wire feed speed rather than chasing voltage fluctuations, making the process easier to manage and more repeatable. While pulsed current can be used as a mode within a constant-voltage system to control heat input, the fundamental voltage characteristic relied on for most GMAW equipment is constant voltage. Constant current would cause the arc to become unstable as the arc length varies, and alternating current isn’t the standard setup for typical GMAW welding.