EVDL Administrator via EV wrote:
On 21 Jan 2019 at 1:18, ken via EV wrote:
What is a 10ths wire?
ten thousands
Wire of any kind or size is not an adequate substitute for a fuse.
Most fuses *are* a piece of wire of adequate size. :-) The trick is in
the choice of wire, and in how it is packaged.
The choice of wire is important. Normal wire sizes aren't that precise;
the variation in cross-sectional area is around %5. Then, due to high
high metal prices, vendors tend to "cheat" (since they know consumers
won't measure it). It's not uncommon to find cheap wire that is 2 or 3
sizes smaller than the package claims.
The purity of the metal is also important. Copper is not a good choice.
Tiny amounts of impurities in copper cause a huge change in its
resistance. Copper also work-hardens; its resistance increases as a
result of flexing. When held near its melting point for long periods
(like a fuse that doesn't quite blow), it crystalizes and develops
stress cracks that significantly alter its resistance. Silver is a
better choice for fuse wire.
The packaging is important. Just like food, if you don't package it
correctly, it will go bad before you can use it. A wire in open air is
subject to being cooled by moving air, heated by surrounding parts,
corroded so its diameter shrinks, and even mechanically stressed if its
ends can move (like a wire between cells that move as they expand and
contract). The ends of the wire matter as well; they can act as a "heat
sink" to pull heat away from the center, so it takes more current to
melt it. So proper fuses are packaged to create a controlled environment
around it.
--
The belief that there is only one truth, and that oneself is in
possession of it, is the root of all evil in the world. (Max Born)
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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