Re: surface area of wire

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

Original poster: "Jim Lux" <jimlux-at-earthlink-dot-net> 


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, September 18, 2003 4:09 PM
Subject: surface area of wire


 > 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.

All those charts and equations all are for idealized situations where you've
got an infinite plane of conductor.  For Litz wire, it's a totally different
story.  Do a google for Litz wire and you'll turn up a paper by a guy who
did a lot of analysis for Litz wire in switching power supplies.

 >
 > 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 ?

You're right.. standard stranded is not like Litz, but then, it's actually
worse than solid. All those small wire/wire contacts

 >
 > 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.

Check the papers on Litz wire and do some calcs before you start.  Then wind
and check.. empirical data is always useful.

 >
 > Many thanks,
 > Chris
 >
 >