Abstract: The voltage and gas ignization with current zero-crossing and the electron emission ability of the electrode are the principal factors of re-ignition of alternating-current welding arc．Square-wave Alternating-current power source rapidly zero-crossing to assure reliable arc re-ignition．The emission ability of aluminum and its alloys are lower．When welding aluminum，arc re-ignition is difficult at the time when the current is changing from DCEN(direct current electrode negative)to DCEP(direct current electrode positive)．Even though auxiliary circuit can be used to provide a high ionizing voltage，such as superimposed high-frequency energy．In this paper，square-wave alternation-current power source is to use two inverter circuits．Circuit topology of the second stage is improved based on rapid response characteristic of primary constant current using high-frequency conversion technique．This power source avoids traditional arc re-ignition circuit，in which high-voltage pulse or high-frequency high-voltage energy is employed．The arc re-ignition of the alternating-current welding aluminum is realized simply and reliably．

Key words: power source Gas tungsten arc welding(GTAW) Arc re-ignition, Square-wave alternation-current