A unit of time equal to one complete cycle of alternating current. In a 60 hertz power system, a jiffy is exactly 1/60th of a second, while in a 50 hertz system it is 1/50th of a second. Engineers and technicians use it as an informal reference for the shortest practical time increment in AC power timing, especially when discussing fault clearance or relay operation speeds.
Heard on the job
The breaker needs to clear that fault in a couple of jiffies or we risk losing the whole bus.
Insider tip
You will rarely see this written on official test sheets, but it is a common spoken shorthand when estimating how fast a mechanical contactor or relay drops out.