Investigation of alleged appliance electrocutions and fires caused by internally generated voltages

Many appliances convert the supply sinusoidal voltage to another voltage or waveform. Evaluation of the possible electrocution and fire hazards, which is important for internally generated voltages such as a single pulse from a capacitor, trains of pulses, direct current, and high voltage alternating current, is reviewed. For electrocution studies, the effect of a periodic output waveform is related to an equivalent 60 Hz sinusoidal electrical shock. The lethal effect for shocks from voltages with periodic waveforms is determined by the frequency components on the human body. Electrical injury is related to the energy in the shock for single pulse shocks. For direct current shocks, approximately three times as much current is required for a given effect on the human body as for 60 Hz shocks. Appliance power supplies can be a source of ignition for fires when combustibles are present. High-voltage current-limited supplies can cause fires when output currents track across combustible surfaces or ignite combustible material between the electrodes