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Re: surface area of wire
Original poster: Ed Phillips <evp-at-pacbell-dot-net>
Tesla list wrote:
> Original poster: "chris swinson" <exxos-at-cps-games.co.uk>
> Hi all,
> I'm considering winding a small test coil with litz wire. I would like to
> know if theres a chart which states the skin depth of wire at high frequency
> in mm. Ive seen a chart in inches floating around though I can only get to
> grips with mm. From what ive found 200khz is around 0.15mm skin depth. It
> would be useful to have exact figures.
> Also, Is there any comparrisons to surface area in relation to solid
> core,multistrand and litz wire ? For example if I have a wire of 1mm dia,
> surface area would say be 3mm, now if I had a 1mm Dia wire with multistrand
> how would that be worked out ? All the wires are shorintg out in all
> combinations so in comparrison to the solid core wire I wouldn't imagine
> multistrand to give much more surface area than solid core ?
> Litz wire would be the best. I plan to build a high Q secondary with this
> wire to see what happens. I have compaired solid core to stranded wire and
> was amazed to find the multistrand coil gave 2" arcs with little input
> power, though a solid wire which should have been better , wasn't and gave
> no output at all. Despite the stranded wire had spaced turns ( due to
> insualtion ) there should be a lot less output since the solid core verson
> was a normal wound secondary. Length of wire and wire dia was as close as I
> could get.
> I think it would make a interesting test since multistrand worked better
> than solid wire. which is why im interested in testing out Litz wire which
> would give me 10times the surface area and should give a much higher Q coil.
> Many thanks,
About thirty years ago I wound a coil (5.25" dia x 18" long) with litz
equivalent to #28 B&S. I couldn't tell the difference between it and a
similar form wound with #28, except that because of the cloth covering
of the litz I didn't get as many turns on it as I with the heavy formvar
wire and the frequency came out slightly higher. Definitely not worth
the bother, at least in my opinion. Remember that once the streamers
start to Q goes so low that wire resistance isn't very important.