OK, I have nothing better to do tonight - so did a little checking
around work (aerospace) and came up with a good fuse reference that
anybody can look at on the ‘net.
Reference: http://www.littlefuse:com, circuit protection 101
(“Fuseology”)
In summary: A fuse will blow depending on the current, time and
temperature. At 25 degrees C, a typical 3AG fuse is required to: carry
110% current rating for 4 hours minimum,
must open at 135% of rated current within 1 hour,
must open at 200% of rated current within 2 minutes
must open at 1000% of rated current within 0.001 to 1.0 seconds,
depending on its type rating.
“The current rating of a fuse is typically derated 25% for operation at
25 degrees C to avoid nuisance blowing. For example, a fuse with a
current rating of 10A is not usually recommended for operation at more
than 7.5A in a 25 degree C ambient.”
Now, add temperature - normal fuses must be derated another 10% and slow
blowing fuses derated about 40% when operated at 100 degrees C (ei:
under the bonnet.)
Lots of useful information at littlefuse.com, buss.com or other fuse
manufactures. (the usual disclaimer applies - just picked names out of
the catalogues.)
----Original Message Follows----
From: DANMAS@aol.com
Date: Mon, 5 Oct 1998 16:17:05 EDT
To: 105671.471@compuserve.com, triumphs@autox.team.net
Subject: Re: Fuses
In a message dated 98-10-05 16:07:36 EDT, 105671.471@compuserve.com
writes:
> I can tell you that here in the US of A when the manufacturer
> rates
> a fuse at 20 amps it means that it is guarrnteed to not blow at 20
amps and
> it is
> guaranteed to open at 40 amps and may or may not blow anywhere in
between.
Dave,
Then that would mean that an American 35 amp fuse will blow some where
between
35 and 70 amps! Scary! I just hope no one is running any of them in
their
Triumphs, thinking they are equivalent to Lucas 35 amp fuses. The
biggest wire
in a Triumph is not capable of handling 70 amps (excluding the battery
cable);
very few are capable of handling even 35 amps.
Dan Masters,
Alcoa, TN
'71 TR6---------3000mile/year driver, fully restored
'71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion -
see:
http://www.sky.net/~boballen/mg/Masters/index.html
'74 MGBGT---3000mile/year driver, original condition - slated for a V8
soon
'68 MGBGT---organ donor for the '74
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