What describes AC operation in GTAW?

• A. It is a compromise between DCEN and DCEP, with heat balanced between work and electrode and high frequency helps maintain the arc
• B. It concentrates heat at the electrode
• C. It eliminates oxide layers completely
• D. It uses no high frequency

Answer: (A)

AC operation in GTAW means the welding current reverses polarity each cycle, so heat is delivered to both the electrode and the workpiece over time rather than being fixed to one side. This makes the process a blend of the effects you get with electrode negative and electrode positive direct current, giving a balanced heating pattern across the cycle. The high-frequency component helps strike and stabilize the arc when the polarity switches, keeping the arc from dying out and aiding a smooth weld pool. Additionally, the positive half of the cycle helps clean oxide on the workpiece surface, which is particularly important for materials like aluminum. So, AC is described as a compromise between the polarities with heat shared between work and electrode, and high frequency is used to maintain the arc during reversal.