What type of welding power source is used for GTAW?

• A. Closed Circuit Voltage
• B. Constant Current
• C. Open Circuit Voltage
• D. Constant Potential

Answer: (B)

GTAW relies on controlling heat input primarily through current. A constant-current power source keeps the welding current near a set value, even as the arc length and arc voltage change during welding. This stability in current produces consistent heat, penetration, and bead shape, which is essential for TIG welding with a tungsten electrode. The arc voltage will naturally vary with arc length, electrode distance, and torch angle, but the current stays steady, giving predictable results.

Using constant voltage or open-circuit voltage would make the current swing as the arc length changes, leading to unreliable heat input and inconsistent welds. Open-circuit voltage is only the voltage present when there is no arc, not how the weld is controlled. Constant potential would keep voltage fixed while current fluctuates with arc conditions, which is not desirable for GTAW. So the best choice is a constant-current power source.