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Re: Help!(with wire size) Please!!




From: 	Geoff Schecht[SMTP:geoffs-at-onr-dot-com]
Sent: 	Wednesday, September 03, 1997 2:04 PM
To: 	Tesla List
Subject: 	Re: Help!(with wire size) Please!!

This discussion brings up the interesting question of skin effect.....has
anybody experimented with winding a secondary using Litz wire? Litz or
multiply-paralleled wires is about the only way to keep ACR (AC resistance)
losses acceptable at 100KHz or above when you're designing a switching
power supply (which is just the grandson of a TC, anyway :) ). My hunch is
that Litz would improve the power output of a TC by improving the broadband
characteristics (i.e., increasing the harmonic power available) of a
secondary. Higher Q would also result. Higher Q is why Litz wire is used in
those loopstick ferrite antennas that even the cheapest AM radios use.

I don't have a copy of my reference books handy but I remember that #26AWG
has a rather high ACR/DCR at 100KHz and above. #36AWG is substantially
better in this respect so at HF you'll get lower copper losses with a
10-wire bundle of #36AWG compared to the losses incurred by a single #26AWG
(a 10x36AWG bundle has almost exactly the same cross-sectional area as a
single #26AWG). At the frequencies that TC's operate at, #32AWG has about
the same ACR as DCR so anything that size or smaller should yield minimal
losses for smaller coils that don't need the current-carrying capability of
heavier wires.

Litz is troublesome in a closed transformer structure since it's bulky (
the individual strands in the bundle are each insulated, of course, plus
the twisting adds a lot of girth). Bulk shouldn't be a problem in a long
open solenoid such as a TC secondary.

Litz can also be expensive. I used to buy it from Kerrigan-Lewis for about
US$50 per pound; it occasionally shows up as surplus. It is possible to
wind it yourself but that's a real chore.


Geoff

> > >
> > >
> > >From:  John Berry[SMTP:antigrav-at-ihug.co.nz]
> > >Sent:  Sunday, August 31, 1997 2:11 AM
> > >To:    'Tesla List'
> > >Subject:       Help!(with wire size) Please!!
> > >
> > >Does anyone know if  .08 mm (circumference) magnet wire is too thin
> > >for
> > >a Tesla Coil  secondary?
> > >
> > >Thank's,    John Berry
> > >
> > >
> > John..
> > 
> >   My wire table indicates .08mm wire to be equivalent to #40 A.W.G
which
> > is a little small for secondary coils,but would probably work OK on a
> > small coil ( wind carefully as that small of wire is easy to overlap).
> > #30 to #26  works well (small coil systems)  but  if all you have is
#40
> > why not give it a try?
> >  Half the fun of coiling is experimentation and using what you have on
> > hand.
> > 
> > Kevin E.
> > >
> > >
> I didn't answer this one earlier because I didn't have a handy way to
> convert mm to awg. Since it is such a small guage, I suggest you wind
> you coil as normal, then wind a second layer on the first one connecting
> both coils together at top and bottom. This gives approximately the same
> number of turns, but at twice the wire cross section. I have read
> several posts on this list where this was done successfully. Good luck
> and be safe!
> -- 
> 
>     Rick Holland
> 
>     The Answer is 42
> 
> 
> 
>