Mark :
The definition of an Ampere has remained the same, however, the method
of rating fuses is/was somewhat different in different parts of the
world.
The original Lucas fuses were rated in terms of maximum fault current.
IOW, a Lucas 50 amp fuse is supposed to blow if you run 50 amps through
it, but may or may not blow if you only run 49 amps through it.
The US standard (which I believe is now used in most parts of the world)
rates a fuse in terms of minimum carry current. IOW, a 25 amp fuse is
supposed to carry 25 amps, but may or may not blow if you run 26 amps
through it. (Obviously, I'm simplifying here. Fuse manufacturers will
share with you all kinds of data on their fuses, including complete
characterization curves, if you ask.)
I found a nice substitution chart on the jag-lover's site :
Simon S. Johnson sends the following data: "...the source: a
1974
edition of "Buss Fuse Car and Truck List" which has on the
back cover a
section call "Foreign Car Fuse Replacement Data," -- foreign
to the US,
that is. It states that "English standards differ from US
standards.
This accounts for difference in ampere ratings." Then it
provides a
list:
English Type Buss Replacement
50 amp AGC 30
35 amp AGC 25
30 amp AGC 20
25 amp AGC 15
20 amp AGC 10
10 amp AGC 7 1/2
5 amp AGC 3
Randall
Mark Gendron wrote:
>
> Ok, I think I got into this conversation a bit late. Are the Lucas fuse
> ratings not directly equivalent to modern fuse ratings? What's the story on
> this? Has the concept of an Ampere changed in the last few decades?
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