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

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wrote:

It isn't. You might generate lightning by a static phenomenon, but if a current flows (ie there's a flash) then it will also generate the magnetic effects.
There's also the question of Tesla coils, which are AC anyway. Most of the museum "lightning demonstrations" you see are done with Teslas, rather than an electrostatc machine. Except in Boston though, where they still have that huge Van de Graaff generator that's sometimes used for "geek in a cage" shows.
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On Sat, 23 Jun 2007 12:02:28 +0100, Andy Dingley

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wrote:

I've never seen busbars much thicker than that, even in DC systems.
I used to work in telephone exchanges, back in the days of Strowger etc. _Lots_ of power was needed to run an exchange, all distributed at 50V DC. The bus bars were copper strip, about 1/2" from memory and up to 12" wide. Generally the thickness was standard everywhere, but the width was proportional to the current for that citcuit. For a really big feed, such as the one from the battery room downstairs, these busbars would be paralleled up and spaced slightly apart. Mainly this was done for ease of mechanically forming busbars, as two 1/2" strips are easier to install than one 1" strip. It also meant thought that skin effect wouldn't have been a problem, even at 50Hz.
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Tom Watson wrote:

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...
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Not with the intent of giving offence but -
That is a particularly shabby piece of reasoning.

Tom Watson
tjwatson1ATcomcastDOTnet (real email)
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Tom Watson wrote:

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.
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ex cathedra v. non cathedra.
is this really the best that you can do?

Tom Watson
tjwatson1ATcomcastDOTnet (real email)
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Tom Watson wrote:

It's really the best (actually more than) it deserves here.
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Catapultam habeo. Nisi pecuniam omnem mihi dabis, ad caput tuum saxum immane mittam.
http://forums.craigslist.org/?forumID
You might try your question there. They really get into this kind of thing there.
todd
wrote:

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Not with the intent of giving offence but -
Yours is a particularly baseless argument, seemingly overly fond of your own insightfulness.
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Tom Watson wrote:

I marked the thread with an OT because I'm trying to be helpful and Tom apparently forgot to do it.
But, as regards the reasoning, I have to agree with Tom. For many years there were some really, really bright people working on heavier than air flight Da Vinci, for one) ... and a couple of bicycle mechanics from Ohio share the honors with a Latin American bon-vivant for solving the basic problems.
While Goddard gets much of the credit for space flight, a lot of very intelligent Chinese had solved most of the problem centuries earlier ... but never finished up.
It's hard to point at any single area of life and say 'IF there was an answer THESE people would know what it is.' I can say it ... but it's hard to keep a straight face.
I do rather suspect that enough research would reveal that the question has already been considered since one of the areas engineers are often found considering is price.
Bill
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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
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<Tom Veatch> wrote in message wrote:

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
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That has the sound of stating that the EE's are missing the obvious benefits of applying these principles universally. As you so properly stated though, they are being applied in the relevant industries. The operative part of that is the word "relative".
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todd wrote:

Tom's trying to oversimplify a complicated question and then produce an engineering design based on that oversimplified analysis.
Electrons in a conductor flow wherever the electromagnetic field in the conductor causes them to flow. At DC levels the field is more or less uniform throughout the conductor so they'll move more or less uniformly through the entire cross section. At AC levels where skin effect becomes an issue the electrons will flow more heavily near the surface than at the center, with the details depending on the geometry, the frequency, and the current.
The trouble with his notion of using "thin coatings" is that there still has to be enough cross sectional area to carry the current. At 60 Hz AC levels, trying to use a "thin coating" for household wiring doesn't gain you anything--the diameter of a solid conductior is much less than the skin thickness and making the conductor a shell wouldn't reduce the amount of conductive material needed, it would just make the conductor more costly to manufacture and more difficult to handle. In substations at very high currents the diameter of the conductor becomes large relative to the skin thickness and it becomes beneficial to use his "thin coating" in the form of tubular busbars. This is also done in the aforementioned aluminum clad steel transmission lines, however in that case the hollow center is in effect filled with the steel structural element.
As for his electrical engineer friend, EEs don't generally deal with electrons unless they're designing vacuum tubes, they deal with fields--for the distribution of electrons in a conductor he'd really have to ask a solid state physicist.
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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
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Tom Veatch wrote:

Certainly, but invention does not take place (so to speak) in a vacuum. No innovation can violate demonstrated physical properties. Maxwell's Equations that describe the governance of electromagnetic fields have been with us for quite some time and seem unlikely to be wrong. So, if we are to "innovate" in matters as discussed here, there are really only two choices: A) There must be a fundamental breakthrough in physics that changes all the known rules (possible but unlikely) or B) We find a better way to engineer around the known constraints of physics.
What Tom wants makes sense, but only in limited contexts, at least as physics is understood today. Moreover, all engineering is a tradeoff between features, time (to go to market) and *cost*. A modern wire manufacturing facility is not a cheap thing to build. To justify what Tom suggest, there has to be concrete economic advantage. If copper cost, say, $3M per oz, that would be a compelling economic driver. But it doesn't and the economics seems - at least at a casual glance - to favor the status quo.
BTW, note that the transition from vacuum tubes to semiconductors was not a fundamental shift in our understanding of amplification or oscillation. It was a fundamental breakthrough in process technology. That is, we discovered how to do what vacuum tubes were doing in a more compact, and ultimately, less expensive way as a matter of *engineering*. There was, of course, a corresponding breakthrough in our understanding of the physics of semiconductors. Even so, semiconductors never completely replaced vacuum tubes. Radio transmitters of any large size still use tubes (valves to those of you in the rest of the Anglosphere) because there are no transistors of which I am aware, at least, than can deliver 50KW of RF into an antenna.
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On Sat, 16 Jun 2007 02:27:09 -0500, Tim Daneliuk wrote:

High-powered radar has been all solid state for some time. Many, many peak KW at low duty cycle into the antenna. Continuous (AM, FM, TV) at high power uses a number of smaller amplifiers with a split feed at the input and a combiner at the output.
Back in 1975, I worked with solid state amplifiers in the ultrasound range (30-50KHz) that delivered bursts of a single tone into a piezo transducer. Several peak KW with two TO-3 transistors and no heatsink!
Today, Harris Broadcast sells an all solid-state 40KW FM broadcast transmitter. I'm sure there are others, and for AM and TV as well.
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Art Greenberg wrote:

Interesting. I used to service marine Radars, and while their peak output power was in the 10-50 KW range, their average power was far lower because of the low duty cycle. When you say that radars have been solid state for some time, does that mean magnetrons and klystrons are no longer in the picture? (Not arguing, just curious.)
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On Sat, 16 Jun 2007 11:24:17 -0500, Tim Daneliuk wrote:

I'm pretty sure that cost still dictates magnetron transmitters in recreational (marine) and virtually all commercial radars. I spot-checked a few Furuno and Raymarine units between 4KW and 60KW, and they use magnetrons. I wasn't able to find any on-line references to klystron based units. I also wasn't able to find any on-line product brochures or other evidence of commercially available all solid-state radars, which surprises me greatly.
Back when I was a little closer to this, in the early 90s, there was work being done to put together all solid-state radar transmitters. But the transistors of that era were unable to do make very high peak power pulses needed for high resolution returns. There was discussion of using signal processing techniques in both the transmitter and receiver to compensate for longer pulse durations. But at the time, that kind of processing was costly. It certainly should be much more in reach today.
I was able to find a few items on-line that talk about military solid-state radar dating to as early as 1992, and a report about an FAA test of a solid-state ASR in 1994.
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