This article describes methods to identify hazards and assess the risks associated with capacitor stored energy. Building on previous research, we establish practical thresholds for various hazards that are associated with stored capacitor energy, including shock, arc flash, short circuit heating, and acoustic energy release.
VI. Risks when a fault occurs circuit power. uncontrolled release of this energy. This systems containing several capacitor units due to possible avalanche effects. 2. Power capacitors can actively fail when internal or external protective devices are missing, incorrectly dimensioned or have failed.
Capacitors may retain a charge long after power is removed from a circuit; this charge can cause dangerous or even potentially fatal shocks or damage connected equipment. For example, even a seemingly innocuous device such as a disposable camera flash unit powered by a 1.5 volt AA battery contains a capacitor which may be charged to over 300 volts.
However, the stored energy within a capacitor becomes a lurking threat. While electrical capacitors have long been recognized in many trades as a potential electrical hazard, historically the National Fire Protection Association (NFPA) 70E standards for electrical safety did not say much about them.
Whether a capacitor can cause injury is mostly related to its voltage rating. If it is not designed or rated to store high voltages, then it won't have enough voltage potential to create a current in a human touching it.
When power capacitors are used, suitable te possible danger to humans, animals and property both during operation and when a failure occurs. This applies to capacitors both with and without protective devices. Regular inspection and maintenance by a competent person is therefore essential.