Development of a Portable Spot Welder

This research is related to the development of a portable spot welding machine as a tool used for joining thin metal parts. In conventional equipment, a transformer is the main power supply working for short duration at low voltage and high power resulting in a large and heavy spot welding machine, not suitable for some applications which require more compact and lightweight units such as offsite maintenance works. Studies show that the Ultracapacitor (UC), which functions as a transformer but works at low-voltage, high-current and high-power conditions, can provide higher power-to-weight ratio than typical iron core transformers. The developed machine would thus offer significant size and weight reduction compared to the conventional spot welders. In this research, 6 units of UC products by Maxwell Technology effectively operating at 2000 F, 2.7 V are connected in series under rated current limit at 15 V, 2000 A. The prototype welder was tested for welding stainless steels sheet having 0.7 and 1.4 mm thickness. It could weld two 0.7 mm thick stainless steel sheets using approximately 1800 J, the power output approximately 31000 W, 2000 A within 0.06 s. Moreover, 1.4 mm thick stainless steel sheets are successfully welded requiring about 3000 J, 29000 W, and 1900 A within 0.10 s.