Which statement about GTAW using alternating current is not true?

Which statement about GTAW using alternating current is not true?

• A. High frequency is for arc starts only
• B. High frequency is for arc starts and arc stabilization
• C. Alternating current can aid arc cleaning
• D. Alternating current requires a compatible power source

Answer: (A)

In GTAW with alternating current, high-frequency energy is used not only to initiate the arc but also to help keep it stable as the current reverses. The high-frequency field ionizes the gas to create a reliable, continuous arc, which reduces arc wandering and makes it easier to maintain a steady weld once start-up is done. Additionally, the positive half of the AC cycle promotes oxide removal on the workpiece surface (arc cleaning), a benefit that's enhanced when the arc is well ionized by high frequency. Because of this, saying high frequency is for arc starts only isn’t true—the same HF capability can aid both arc stabilization and cleaning during AC GTAW. The other statements describe true aspects: AC can assist arc cleaning, and a compatible power source is needed to support the HF function.

In GTAW with alternating current, high-frequency energy is used not only to initiate the arc but also to help keep it stable as the current reverses. The high-frequency field ionizes the gas to create a reliable, continuous arc, which reduces arc wandering and makes it easier to maintain a steady weld once start-up is done. Additionally, the positive half of the AC cycle promotes oxide removal on the workpiece surface (arc cleaning), a benefit that's enhanced when the arc is well ionized by high frequency. Because of this, saying high frequency is for arc starts only isn’t true—the same HF capability can aid both arc stabilization and cleaning during AC GTAW. The other statements describe true aspects: AC can assist arc cleaning, and a compatible power source is needed to support the HF function.