ee's please reply - (or those who think think they may know)

[dpb]

Trust me, there are some _REALLY, REALLY BRIGHT_ folks who do this stuff for a living -- if it were feasible, they would have already done it...

--

[Tom Watson]

Tim:

Let's say that I admit all that you present.

The fundamental question still stands.,

Why do we >Tom Wats>>

Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

[Tom Watson]

Not with the intent of giving offence but -

That is a particularly shabby piece of reasoning.

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

[WoodButcher]

At DC the entire volume of the conductor is carrying current, not just the surface. The DC resistance of a conductor is: R = [bulk resistivity] x [length] / [cross sectional area] In the above area is independent of geometry. It works for round, square, triangular, etc. If current only flowed on the surface the above equation would have the wire circumference in it instead of area.

For AC skin depth is a factor as others have already pointed out. Changing the geometry of the conductor, from a rod to a sheet, is one remedy for this. Litz wire is another and it is good for up to about 1MHz IIRC.

Art

[Tim Daneliuk]

Several reasons leap to mind:

1) The place where you typically most care about efficient current conduction (i.e., where resistive losses matter especially) is in high power applications. These typically are in the 50-60Hz range where skin effect is negligible. 2) The complexity and cost to manufacture what you suggest was either impossible or so economically irrational that it was never pursued historically. Even today, with quite sophisticated manufacturing process technologies, is it really worth it to, say, make a better coax to go from cable converter to your TV? The currents (and losses) involved are miniscule and almost certainly pale by comparison to the costs to spin up a new wire manufacturing facility. 3) In effect, what you ask for is already taking place. In high frequency applications like VHF/UHF radios and microwave Radar, there is a technique called "microstripline" that uses the copper etching on a circuit board (thin but with appropriate area) to actually synthesize discrete components like capacitors and inductors. This has been done for years. But note: These are very high to microwave range frequencies where skin effect does indeed kick in AND the places where microstripline is used tends to be medium to low power environments - say under 500 watts or so (at least that's my last recollection - things may well have changed in the intervening eons). 4) As someone already pointed out - the Public Futilities have a deep and vested interest in reducing cost and improving reliability of their plants and transmission facilities. They have many Smarty Pants Engineers (tm) who look at exactly these questions. If/When there is a compelling economic driver to do this, you'll see it happen. Again, though, they live at 50-60Hz so it's not likely ...

---------------------------------------------------------------------------- Tim Daneliuk [e-mail] PGP Key:

[Mike in Arkansas]

[Markem]

Experimenting with light weight conductors is always being done. But the holy grail is room temp super conductor. The skin effect does happen but at the diameter of the conductors generally used it is not a problem (DC current). The electrons are forced in a random pattern similar to the way photons travel within the suns deepest layers changing from atom to atom within the conductor, but with a very limited area.

But as Davis Estep once told me in my beginning of my tech career, either it is forward biased or not.

It works or it does not.

Not an EE, but a eclectic electronic technician of over 25 years.

Mark (sixoneeight) = 618

[Doug Goulden]

Look up wave guides, as frequency reaches Giga hertz range the current passes along the skin. Radar frequencies actually travel inside a hollow conductor that "funnel" the signal from the electronic circuit output to the antenna.

[Morris Dovey]

Tom Watson wrote: | There have been a number of responses so far, many of which | reference the "skin effect" - why the hell do we continue to | produce wire that has a core of the same conductive capacity as the | surface, at great cost, when we might manufacture a wire of a | cheaper core material, with the surface conductor at optimum.?

It's already been/being done. Check out wire for electrified fences at your local farm store. Mild steel core with copper exterior. I used it for building VHF transmit/receive antennas.

One more thing: VHF antennas work better when (a) wire diameter is increased and (b) the wire is polished mirror bright.

-- Morris Dovey DeSoto Solar DeSoto, Iowa USA

[todd]

I used to work in an industry that catered to the electric utility industry, specifically in transmission and distribution. If there was ever an industry where this would matter, this would be it. The concept of, for lack of a better term, bimetallic cable is not foreign to this industry. The have a variety of cables classified as ACSR (Aluminum Conductor, Steel Reinforced). These cables contain a stranded steel core with a stranded aluminum covering. Now, the purpose of this is not for cost reduction, but in high-strength applications where aluminum or aluminum-alloy conductors would not be strong enough. My assumption would be that since the engineers are familiar with this product and its current-carrying capabilities (and how it relates to AAC and AAAC conductors), if there was an advantage to this sort of arrangement, they'd be doing it. From your other posts on this thread, it appears that you think it just hasn't occurred to them to check. That might be the case, but I doubt it.

todd

[dpb]

It's true, however...as someone else has noted, if it were economically feasible, it would have been done a long time ago as the actual concept does exist.

You, of course, in your infinite wisdom, are welcome to enter the field and make your fortune in an area others have overlooked.

--

[Tom Watson]

Don't know whether they thought to check, or not.

Don't really know how someone who isn't really creative via personality might be encouraged to think outside the box created for them - that made them part of their personal cognoscenti.

If you teach a non creative person that x is true, he will think that x is true.

He may pass his whole life without questioning what x is.

I've played with drummers who are like that.

Go back to the initial question and see if you can answer it.

So far, I haven't seen any satisfactory answers.

Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

[Tom Watson]

ex cathedra v. non cathedra.

is this really the best that you can do?

Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

[dpb]

It's really the best (actually more than) it deserves here.

--

[Tom Veatch]

When vacuum tubes were coming on line, there probably wasn't an awful lot of funding for semiconductor research. "Invention" may be what's needed rather than "development".

Tom Veatch Wichita, KS USA

[Tom Veatch]

Believe me, I'm not trying to be a wiseass, but there were some "REALLY, REALLY BRIGHT" folks in the 1800's. So why didn't they "already done" semiconductor devices?

The point is, we don't know all there is to know about (fill in the blank). Right up until Kitty Hawk really bright people were insisting that heavier than air powered flight was impossible - even though gliders had been around for years.

Tom Veatch Wichita, KS USA

[todd]

Ease up on the analogies. We're not talking about having to invent a superconductor. The actual products that Tom is wishing someone would use are already in existence in relevant industries, they're just not being used in quite the way that Tom is contemplating. It's just that electrical engineers aren't creative enough to connect the dots.

todd

[Robatoy]

On Jun 15, 7:43 pm, Tom Watson wrote: [snipped for brevity]

Please add some more information:

1) define 'thick' ('thickness' can be manipulated via the increase in voltage carried.... jack up the voltage high enough, and I can push a whack of power through a wire the size of a human hair.) 2) at what frequency, or range of frequencies?

r

[todd]

Catapultam habeo. Nisi pecuniam omnem mihi dabis, ad caput tuum saxum immane mittam.

might try your question there. They really get into this kind of thing there.

todd

[Leon]

IIRC in 6th grade science class I learned that the energy travels on the outside of the wire.