Solving Critical Issues at Low Current in TIG Welding by Controlling Levels of Saturation at the Input of the Inverter

Abstract

The operating current range for TIG welding is wide. Welding at very low current in TIG mode is common. However, managing low current operation in dynamic situation is critical. High frequency inverter has the extra ability to take care some of these problems to a great extent. To meet such requirement(s), the amplifier for the inverter is normally a ‘P+I’ controller with large DC gain. The bandwidth of this type of inverters is limited by the presence of lag compensating elements of the controller. However, lag compensator with ‘controlled peak current mode control’ can develop, to our advantage, ‘wind-up’ in the controller to bring benefits on the dynamical aspects for TIG welding inverters at lower current setting. This paper would discuss the issues of TIG welding at low operating current and also demonstrate how wind-up is created to eliminate the problematic issues. It is absolutely critical for non-contact TIG welding inverter.