To which voltage electrical circuits are GTAW machines typically connected?

GTAW (Gas Tungsten Arc Welding) machines, commonly known as TIG welding machines, are typically designed to operate at both 120 V and 240 V. This dual voltage capability allows for versatility in different welding environments, whether they're in residential settings or industrial applications. Many small or portable GTAW units can run on standard household voltage (120 V), making them accessible for home-based projects or light industrial tasks, while higher power applications in more demanding industrial settings often require the use of the 240 V supply.

The other voltage combinations provided in the options do not typically align with the standard operating voltages for commercial or residential GTAW machines. While some welding equipment can operate at higher voltages, the combination of 120 V and 240 V is the most common for GTAW applications, making it the correct answer for this question.