Welding is an important manufacturing process that can be automated and optimised. The dynamic characteristic of a self-regulated, consumable electrode welding arc has been studied when the torch-to-work-piece distance varies with time. The self-regulation process have been modelled analytically and various dynamic models have been developed. Computer simulations have been used to obtain a better understanding of the mechanisms which change arc voltage and current in response to changes in arc length. A welding current fuzzy controller has been proposed.