Abstract
In this paper, a power controller and 3 phase voltage source inverter are proposed for the improvement of weldability of large scaler Mash seam welder. The welder system is designed for the low cost and the improvement of weldability. For this system, the thyristor convertor has performed constant current controlling in the output terminal by using PAM type inverter. We have simulated our algorithm and made a prototype welder for experiment. Through the experiment, we have confirmed the improvement of weldability of our system.