Re: Electrical Properties of Brass

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

Original poster: "Gregory Hunter by way of Terry Fritz <teslalist-at-qwest-dot-net>" <ghunter31014-at-yahoo-dot-com>

Terry,

That's really interesting! Can you do a similar
analysis of aluminum roof flashing? I've often thought
about cutting it into 1" ribbon and using it for
primary coil stock.

Regards,

--- Tesla list <tesla-at-pupman-dot-com> wrote:
 > Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>
 >
 > Hi Jeremy,
 >
 > Resistance = Resistivity X Length / Area
 >
 > The numbers I have here are all in meters.
 >
 > Copper = 1.7 x 10E-8  Ohm-Meters
 > Brass = 6.39E-8 Ohm-Meter
 >
 >
http://www.matweb-dot-com/search/SpecificMaterial.asp?bassnum=MBRASE
 >
 > So brass is about 4X more resistive than copper at
 > DC.
 >
 > Skin Depth = 1 / SQRT(pi x f x Resistivity x
 > Permeability)
 >
 > Permeability = pi x 4e-7  H/m  X  Ur
 >
 > Ur copper = 1
 > Ur brass = 1.05
 >
 >
http://www.npl.co.uk/electromagnetic/dclf/magnetics/lowpermeabilitylc.html
 >
 > So the skin depth is about 1/2 that of copper since
 > the resistivity is 4X.
 >
 > The skin depth of copper is 2.602 / SQRT(F) inches.
 > At 154kHz that is
 > 0.00663 inches.  So brass is roughly 0.0033 inches.
 > Your 16mil brass is
 > perfect.  At 2 inches wide, it is about the
 > equivalent of 0.159 inch copper
 > tubing.
 >
 > So I will say your brass strips will be about 50%
 > more lossy than 1/4 inch
 > copper tubing.  Lots of "if, ands, ors, and buts"
 > too all this... but the
 > brass will work "ok" for a 15/120 NST system.  You
 > may loose about 2 to 4
 > inches as compared to 1/2 inch copper tubing or
 > something but probably not
 > a big deal.
 >
 > Cheers,
 >
 >          Terry
 >
 >
 >
 > At 04:28 PM 4/18/2003 -0700, you wrote:
 > >Hi!
 > >
 > >I was wondering if anyone has any experience with
 > >building primaries out of brass instead of copper?
 > >I want to use brass since I'm worried about copper
 > >oxidizing over time.
 > >
 > >I have a design in mind that is going to use
 > >brass strips for all connections in the tank
 > >circuit. (Including the primary)
 > >
 > >The brass strips I have in mind are approximately
 > >.016" thick by 2" wide.
 > >
 > > >From calculations I have done with JavaTC,
 > >the tank current at gap conduction is going
 > >to be approximately 800 Amps.
 > >
 > >(15KV/120mA NST .03 uf LTR primary cap)
 > >(154kHz resonant frequency)
 > >
 > >I am concerned that the brass strips I've got
 > >are too thin to handle this current load.
 > >Unfortunately, anything thicker is tough to work
 > >with and bend into the proper shapes I require.
 > >(Doubling up the thin strips is an option but
 > >I don't want to do it if i don't have to.)
 > >
 > >On the otherhand, since the tank current will be
 > >oscillating at RF frequencies, skin-effect tells me
 > >that the thickness isn't as much of an issue as the
 > >actual surface area.
 > >
 > >I guess the real question is, how far does a charge
 > >of 800A penetrate into brass at 154kHz ?
 >
 >


=====
Gregory R. Hunter

http://hot-streamer-dot-com/greg

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