Case-Based Safety Analysis of Electric Shock Accidents In Modified Electric Welders using Microwave Oven High-Voltage Transformers

This study investigates electric shock accidents involving non-standard electric welders manufactured by modifying microwave oven transformers, a trend that has been increasingly observed in DIY(do it yourself) high-voltage equipment usage. Two fatal electric shock incidents were analyzed, both of which involved welders lacking basic electrical safety designs such as insulation and protective circuits. These structural deficiencies were identified as the primary causes of the accidents. Experimental measurements revealed that the open-circuit voltage at the secondary side of the modified welders exceeded 2,000V, far surpassing the safety limit of 95 V specified in KS C 9602:2007. Simulations of human body resistance, using enamel resistors ranging from 1kΩ to 5kΩ, demonstrated that the current varied with resistance. Notably, at 1kΩ-a representative value for human body resistance under moist or conductive conditions—an alarming 1.2 A of current was recorded. The victims’ hands showed severe burns and carbonization, indicative of sustained high current flow through body tissues. This study proposes institutional enhancements in safety regulations and distribution control measures. The findings provide foundational data for the establishment of effective safety management systems to prevent severe electrical accidents associated with unauthorized high-voltage equipment.