RE: [VAL] 40 Amp Fuse

[root <geraldj@xxxxxxxxxxx>]

Digging into my fuse data books (2" notebook with more than that of
catalogs) I see this: The three letter fuse types are typically from
Buss Fuse. The first one I opened doesn't admit an AGP, but does show
the AGU which is 13/32" in diameter.

The AGC fuse family goes up to only 30 amps which is plenty for the
contact area of the 1/4" diameter fuse. These are 1-1/4" long and
commonly used for vintage automotive and electronic applications. The
types MDL, ABC, GBB, and MDA are workable replacements up to 30 amps and
some are even UL listed above 20 amps. Many are not. In earlier years
and in other makers these 1/4 x 1-1/4" fuses were sometimes called 3AG,
or 3AB.

In this catalog the AGU fuses go only to 30 amps, and similar rated
fuses (generally higher voltage which isn't a big problem) include BAF,
BAN, KTK, KLM, FNM, and FNW. Older designations included 5AG or 5AB. The
KTK and KLM fuses will be astronomically priced. An older catalog also
shows a MDR being 13/32" x 1-1/2" and going to 40 amps.

In one old catalog it says for 9/32" diameter fuses, "These fuses in
sizes larger than 30 ampere are not recommended as clip or fuse holders
will not permit the fuse to carry such high currents."

I've checked my electrical and electronic catalogs back to the early
1960s. No one admits to making the AGP fuse. I find AGS in 9/32"
diameter, also 5AG.

Small diameter fuses rated at more than 20 amps are poor designs. The
contact area of the fuse clip is marginal at the higher currents and so
will warm up or heat and since the fuse works on heat, poor contacts can
speed up the fuse's blowing.

What are the dimensions and markings on the AGP fuses you have blown?

Gerald J., WBCCI #5623, VAC.