38 2. Literature review and problem statement The TIG-AC process (Tungsten Inert Gas-Alternating Current) is often used to weld aluminum alloys, in which the AC electric arc burns between a non-fusible tungsten electrode and an aluminum article. The voltage on a welding arc over one half-period may differ from the voltage over another half-period due to the different emission properties of the electrode and the article's metal. Because of this, a DC current component emerges in the welding circuit, which can be up to 70-80 % of the working welding current [2]. This component of the welding current causes the magnetization of the core of the welding transformer, which leads to the growth of the magnetization current and to overheating the transformer. The DC component of the secondary current of the welding transformer can be eliminated by including a capacitor battery into the welding circuit [3]. The advantage of this technique is the ease of implementation. The drawbacks of the technique: complexity of weldin 23 g current regulation, poor mass-size indicators, impossibility to ensure a quality welding process without the use of expensive equipment, low reliability of equipment (battery of electrolytic capacitors).