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Re: (ET) Fuse fireball--warning
At 05:06 PM 1/1/06 -0500, Chris Zach wrote:
Well, that was interesting.
I've been using the Saft BB600's in 360 volt battery blocks to power my
Elec-trak. I installed a set of 30 of them in the rear utility box as an
extra power supply. As is custom I installed a 300 amp 48 volt fuse (DC
rated) from a Cushman golf cart between the two strings of 15 batteries.
I recently bought some automotive master fuses, 100 and 120 amp rated.
Mainly because I want a slightly lower fuse rating. These fuses are
rated to clear 120 amps at 32 volts.
Two things to keep in mind here.
- The voltage rating. Auto fuses are typically specced as 32V
MAXIMUM. That's adequate for a 24V battery pack but not above. Above
rated voltage arcing is quite possible, so are explosive failure
modes. And either of those could well cause fire.
- The interrupt rating. This is the maximum current the fuse can
safely disrupt. This is usually much higher than the rated current. If
you exceed this you potentially run into arcing as you would exceeding the
voltage rating.
John mentioned time to blow rating for fuses. That can be an issue if you
are close to the rating but I think you probably ran into the voltage
rating given the description above.
Little fuse has a good discussion on this
http://www.littelfuse.com/data/Product_Catalogs/AUTOFUSEOLOGY.pdf and
especially
http://www.littelfuse.com/data/Product_Selection_Guides/Fuseology.pdf
A rather more obscure but important note from the second reference is an X
amp fuse has different requirements depending on the standard it is rated
under. (see page 6)
For instance take a 100A fuse
Under UL/CSA 284-14 it must not fail for at least 4 hours at 110A , take no
more than 60 minutes (yes minutes) at 135A and no more than 2 minutes at 200A.
Under IEC type F, it must not fail for at least 60 minutes at 150A at must
fail within 2 minutes at 210A.
Note that not only are the standards different but they are mutually
exclusive.
I would suggest sticking with tried and true EV fuses and stay away from
automotive fuses for tractors. Somewhere I've got a link with some tests
Littlefuse did on standard automotive blade fuses for 42V Vehicle
testing. The difference between using standard blade fuses and properly
rated fuses is rather dramatic.
Robert
" 'Freedom' has no meaning of itself. There are always restrictions, be
they legal, genetic, or physical. If you don't believe me, try to chew a
radio signal. " -- Kelvin Throop, III
http://www.aeolusdevelopment.com/