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Re: Balancing L/C Sizes



Original poster: "William Swanson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <swansontec-at-yahoo-dot-com>

Hi All,
Looks like Iíll have to retract my last statement
about wire size not making a difference, since I
overlooked one important little detail. When you use
twice as many turns of wire that is half as thick, you
are actually using twice the length of wire. I didnít
take this into account when I made this statement
about wire size, so it turns out that Iím wrong, and
smaller wire does have greater losses. However, as
somebody else pointed out, after a certain point the
skin effect takes hold and causes the decrease in
resistance for a given wire size to decrease only
linearly. Once this limit is reached, wire size
becomes unimportant, but below this limit, it is
important. Perhaps this is the reason for the rule of
that says you should stick with 22 gauge wire for your
secondary...

Sorry for the goof up.

-William

--- Tesla list <tesla-at-pupman-dot-com> wrote:
> Original poster: "Scott Fulks by way of Terry Fritz
> <twftesla-at-uswest-dot-net>" <darkthing-at-earthlink-dot-net>
> 
> William wrote:
> > wire gauge shouldn't make much of a difference,
> since
> > you can get twice as many turns with wire that is
> half
> > as thick. Since twice as many turns means four
> times
> > the inductance, while half as thick wire makes
> four
> > times the resistance, the inductance/resistance
> ratio
> > stays the same no matter how small your wire is.
> 
> This is not strictly true, due to the "skin effect"
> at high frequencies.  As
> the wire gets thicker, only the outer surface
> conducts the HF current, so
> for thick wires the resistance increases in inverse
> proportion to the radius
> of the wire, rather than the radius squared.  Oddly
> enough, this means
> thinner wires are more efficient carriers of current
> in TC secondaries.
> 
> As an example, at 100 khz, only the outer .2 mm or
> so of wire conducts
> effectively, so any wire gauge heavier than 26
> (radius of .2 mm) will start
> to lose efficiency.  The thicker wire has a lower
> inductance to resistance
> factor (Q) on a given coil form than the thin wire.
> 
> However, most coilers seem to use the "1000 turns"
> rule, which makes this
> argument less relevant.  For a fixed number of
> turns, the thicker the wire
> the lower the resistance at any frequency.
> 
> Regards,
> Scott Fulks (darkthing-at-earthlink-dot-net)
> 
> 
> 
> 


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