Jay Summet via EV wrote:
Is it correct to assume that a 40 amp fuse rated for 240-600 volts will also work just fine at 12 volts? (but not the other way around....)
It will work, but will also have a higher voltage drop. Small, low-voltage fuses generally have less DC resistance than a high-voltage fuse with the same current rating.
Fuse current: The rated current for a fuse is the current at which it will *blow*... eventually. So a 30-amp fuse will blow at 30 amps; but it may take hours (or even days) to do it.
It needs a significantly higher current to open quickly. The fuse's data sheet will specify how much current, and for how long. The time to blow versus current is roughly proportional to current squared x time = constant. Here's the data for a Bussman ABC-30 fuse (30 amp, 125vdc, 1.25" x 0.25" dia.) which I happen to have handy:
100% (30 amps) eventually 110% (33 amps) 4 hours minimum 135% (40 amps) 60 minutes maximum 200% (60 amps) 2 seconds maximum I^2 x T = 1429 0.14v drop at 30 amps 60 amps for 1 minute -- Knowledge is better than belief. Belief is when someone else does your thinking. -- anonymous -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
