A power balance technique for high power welding machines with modular design

This paper presents a power balance technique for high power welding machines with a modular design using a common-mode-coupled inductor (CMCI). The voltage applied across the CMCI can automatically adjust current slopes of transformer primary currents to be equalized so that the power transfer between power modules can be balanced even in the structure in which both the primary side and secondary side are parallel. To show the operation of the proposed method, an analysis has been performed with a welding machine with two transformers and design equations for CMCI has been derived based in the analysis. The feasibility of the proposed method is verified using a 20 kW welding machine consisting of two 10 kW modules.