An arc-fault circuit interrupter (AFCI) is a device intended to provide protection from the effects of arc faults by recognizing characteristics unique to arcing and by functioning to de-energize the circuit when an arc fault is detected.
An arc-fault circuit interrupter distinguishes between a harmless arc (incidental to normal operation of switches, plugs, and brushed motors), and a potentially dangerous arc.
Conventional circuit breakers only respond to overloads and arc circuits, so they do not protect against arcing conditions that produce erratic, and often reduced current. AFCIs are devices designed to protect against fires caused by arcing faults in electrical wiring. The AFCI circuitry continuously monitors the current and discriminates between normal and unwanted arcing conditions. Once detected, the AFCI opens its internal contacts, thus de-energizing the circuit and reducing the potential for a fire to occur.