Nonlinearities in 12-gauge Copper Wire

wrote:


12 ga copper: fusing current is given as 235 amps in Reference Data
for Radio Engineers.

John

Tim Wescott wrote:

melt is hard - you'd need to look at the heat convected & radiated away.

vaporise is easier (except what do you mean by vaporise?). I'd just
assume and adiabatic process, with heating evenly distributed throughout
the material, and do an m*cp calculation for some dT above the melting
point. that'll tell you how much energy you need, which can be worked
back thru R (varying with temperature) to get I for a given t.

and do you drive it with a current or voltage source? the current source
will melt far, far faster due to thermal runaway....


stick it in a bucket of water, and watch it get a lot more nonlinear.
You'll have to navier-gate your way around stokes and stokes of nasty
equations. Oops, I'm prandtling....

Cheers
Terry

Terry Given wrote:

Good point.  And I believe from the names you're throwing around you're
only accounting for convection, not the onset of boiling (and is it a
sealed vessel, where the boiling point & therefore the heat transfer
rate will change with pressure & therefore temperature?)

I was also pondering a section of the same piece titled "common
nonlinearities", then I realized that I'm either going to have a very
few or a book-length report.  Oh well, something to keep me awake at night.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Tim Wescott wrote:

oh yes. by comparison, electronics is easy.

a buddy of mine used 5A fuse wire in a bucket of de-ionised water as an
ultra-fast 400A fuse, while developing an SCR inverter for his PhD. As
soon as the water boiled, *wham* blown fuse. an awful lot cheaper than
the real thing.