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Re: 8 kHz Tesla Coil



Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 06:27 AM 10/1/2005, Tesla list wrote:
Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>


Hi Jim,

I just reread your posting and I'm thinking you are using the skin depth of a flat plane conductor in the equations I quoted. I think those equations are using a skin depth for a round wire instead of a flat plane in which the equation for skin depth you quoted would not apply. I dont know if such an equation exist in reality but the site I'm quoting from gives a SD for round conductors that seems to give a little larger value than what Bart's JAVATC program calculates. Several people in this group said that the SD of a round conductor was different than for a flat plane.

Maybe the real question is: if there was a round conductor skin depth equation, would "what I quoted" be true.

Sure.. but there's no simple equation for "skin depth in a round conductor". Whether you start with the flat plane skin depth (which is simple) and have some wickedly complex equation to figure out Rac, or have a simple equation for Rac, and a wickedly complex skin depth equation, it's really immaterial.


The hard part is accounting for the geometry, not the exponential constant.


If you calculate the resistance of the flat plane conductor that is only one skin depth thick using the flat plane skin depth value, you get the AC resistance. So, is it possible to do the same with a round conductor using a round conductor skin depth??? Some web sites seems to think so. See comments below.

Some websites seem to think so, but are perilously light on the analytical backup for their assertions.




However, those 1-2 mm diameters (approx AWG18 - AWG12) where both approximations are most inaccurate are also those sizes likely to be contemplated by high power coil builders who are most concerned about efficiency.

Not sure what the final answer is other than using the RDRE tables (assuming these are based on measurements and should be considered accurate). Right now I think the only info provided by any of the TC programs is Rdc. Maybe an estimate would be better than nothing. Maybe the RDRE table info could be incorporated into the programs if an equation can not be found.


They aren't based on measurement, but on long tedious analysis and calculation, as far as I know. But, you are right, anything is better than nothing.