Fuses & Fusing

[PEU186F]

I have recently seen a suggestion that, at the time the majority of our cars were built, it was Lucas's practice to rate their glass fuses by the rupture current, i.e. the current at which the fuse would "blow".

Whereas current practise is to rate fuses (including apparently identical glass fuses) by the rated current of the protected circuits, which might be aprroximately half the rupture current

This implies that the replacement of original 35 Amp fuse, designed to rupture at 35 Amps, with its modern equivalent, bought over the counter, would mean that one would be fitting a fuse that would only rupture at approx 70 Amps, which I frankly find a bit frightening.

I would be most interested in anybody else's views on this subject, as I would be happy to be told I've got the wrong end of the stick.

Roger Morrall