The soft switching inverter technique could solve the IGBT easily broken problem. The series have the function of regulating staring arc current and thrust current; it is easy to start arc, with stable arc and good weld bead. Arc thrust can be adjusted as changing the cable length. Remote welding is available. Small volume and weight and lower need of electricity. ZX7-ST series can be used in every walk of life: electric power construction, nuclear power setting, petrochemical production and piping construction. They are designed for two kinds of welding methods: electrode arc welding and argon arc welding. ZX7-400B series can realize downwards-welding by using cellulose electrode. Multi-stations DC arc welding machine can be produced if required. Available remote control box.