Safe Distances From a High-Energy Capacitor Bank for Ear and Lung Protection

Abstract

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A complete electrical arc hazard classification system and its application

“…Acoustic pressures from facility type arcs was first highlighted in 1979 [32] and discussed in several subsequent publications [33][34][35][36]. Acoustic pressures in fast rise time arcs results in super sonic wave fronts and has been studied related to lightning and capacitor bank discharges, which occur in the order of microseconds [37][38][39][40]. 4) Shrapnel results from the high currents that melt electrode materials, and acoustic and magnetic forces that dismantle and propel parts, especially metal parts [36].…”

“…An approximate estimate for sufficient energy to create sparks, reaching the eyes, would be 100 J; for sufficient energy to create an arc flash of 1 cm, would be 20 J; for sufficient energy to create an arc flash of 10 cm, would be 2 kJ; for sufficient energy to create an arc flash of 100 cm, would be 200 kJ; and, sufficient energy to injure the ears from a fast rise time capacitor discharge, would be 20 J (assumes 1 % probability of injury, 50 % conversion to acoustic energy, and 45 cm working distance [39]. Acoustic energy injury thresholds for continuous arcs (e.g., an arc welder) are likely much higher (5 kJ per second) and for a slow impulse arc from a 60 Hz source, perhaps 20 kJ.…”