Wind up and controlled saturation through graded peak current Limit control generates superior performance in wide range TIG welding inverter

摘要

The operating current range of tungsten Inert Gas (TIG) welding is wide. The arc characteristics for such wide current range offer change in control parameters that includes large non-linearity. Extending the current range further down, in TIG, makes the equipment versatile. Non-linear arc characteristics shift the load line drastically at low current region. High gain P + I control is traditionally used for accurate current control. The adverse arc characteristics at low current aided by the high gain system with large saturation limit makes the system oscillatory at very small current. This article would practically demonstrate that the existing controllers are not equipped to handle certain low current TIG operations such as transition process, in particular. This paper proposes a set of solutions to handle the low current control by imposing controlled input saturation. Creation of wind-up and controlled saturation helps achieve superior arc initiation and subsequent transition to welding.