Is continuous HF required to start and maintain the arc when welding with AC in GTAW-P?

• A. Yes
• B. Only for DC
• C. Not required
• D. For AC only at start

Answer: (A)

In AC TIG welding with pulsed current, the arc has to deal with polarity changes every half-cycle, which tends to cause the arc to extinguish when the current crosses zero. High-frequency energy ionizes the gap and provides a ready-made conductive path, so the arc can re-ignite immediately as the current rises again on the next half-cycle. With GTAW-P, you want the arc to stay stable through both the high-peak and background portions, and continuous HF helps maintain that stability, especially on metals like aluminum that form oxide layers that resist ignition. So using HF continuously across the AC cycle keeps the arc alive and steady, rather than letting it die between half-cycles.