ESAB DTA 400 AC/DC is a compact double-current power source, designed for TIG welding and MMA welding with direct and alternating current. The power source delivers an exact square wave at alternating current and a very smooth and stable current at direct current welding. A 3-phase connected main transformer with series-connected thyristors controls the 3-phase rectifier both for direct current and alternating current welding (square wave). A series-connected thyristor inverter allows stepless control within the entire setting range.