Hi Richard:
> why cant the 3 amp only be marked?
> its the lower current rating
> thus best protective of a product,
1. A 3-amp fuse is not readily available
outside North America. Most people
want to replace a fuse NOW, and not
wait for a special order.
If a 3.15-amp fuse provides equal
protection, then a marking indicating
both ratings satisfies users through-
out the world.
2. A lower current rating does not
necessarily provide the best protection.
The fuse rating is selected on the
basis of the consequences of a fault
condition. For fault currents below
the fuse rating (yet more than the
input rating), other safeguards must
provide protection against fire or
whatever other hazards may exist.
The fuse is a safeguard only for fault
currents exceeding the fuse rating.
An excessively low current fuse may
operate on normal current spikes,
and thus be a nuisance by requiring
frequent replacement. This may
prompt the user to replace the fuse
with one of a higher rating, which
in turn may compromise the safety of
the product.
> many labels of ratings for equipment
> state 110/220, yet, you only see the lower
> voltage's ( 110)'s current(higher) rating on the product,
> please educate me why this fuse situation
> is more critical/important than a units overall current
> marking stamped on the power ratings.
The input current rating is a normal-
condition current. The fuse rating is
selected to limit the maximum fault-
condition current.
The input current rating of the product
is used to choose the current ratings of
many primary-circuit components such as
appliance couplers, switches, wire size,
power cord size, etc.
It also gives the user an idea of the load
on his mains distribution system.
Best regards,
Rich
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