surface area of wire

["Tesla list" <tesla-at-pupman-dot-com>]

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,
Chris