Re: AFCI Theory of Operation
Arcing can start and stop spontaneously. With AC, the voltage waveform passes through zero, so the arc can cease on it's own. (With DC, the arc is much more difficult to extinguish since there are no zero crossings. You never want to use AC equipment that is intended for circuit interruption on a DC circuit unless approved for the purpose. AC fuses, for example, rely on zero crossings to extinguish the arcing when the elements fuse. Inside fuses, some arcing is good, since the rising arc voltage reduces current flow.)
But once an arc starts, it tends to be self-promulgating. Heated gas/plasma is conductive, and can result in more arcing. The carbon given off as a result of the hot plasma charring nearby products (conductor insulation, rug fabric, wood framing) is conductive, and can lead to more arcing. The burning/burnt insulation is no longer insulating, and can result in more arcing.
What was the question?....