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Re: twin coil transmission lines (fwd)
Original poster: List moderator <mod1@xxxxxxxxxx>
---------- Forwarded message ----------
Date: Wed, 30 May 2007 14:16:00 -0700
From: Jim Lux <jimlux@xxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: twin coil transmission lines (fwd)
ADate: Wed, 30 May 2007 14:54:42 +0000
>From: David Rieben <drieben@xxxxxxxxxxx>
>Subject: twin coil transmission lines
>I have a question regarding the transmission lines between large
>twin coil systems that's been bugging me for a while now. I have
>never seriously considered building a large twin coil or magnifier
>system, mainly due to the large space that one of these systems
>eats up when assembled. However, I know that there's also
>considerable line losses in the transmission lines that carry the RF
>currents from the SG and capacitor to the primary coil(s) and that's
>the reason that we usually try to keep the tank circuit wiring
>between the SG/capacitor to the primary coil as short as possible
>in a basic 2-coil SG system.
Maybe the losses aren't all that huge, in comparison to other
losses... Let's gedanken this a bit...
Say you're running at 100kHz, and you're using 2cm diameter copper
tubing as your conductor. Skin depth is 200 microns or there abouts,
and the tube is "large" compared to the skin depth, so we can treat
it as a sheet 6.28 cm wide and 200 microns thick, 0.126 square cm
cross sectional area.
Let's further assume you've got 5 meters of line (2.5 out and 2.5
back). So, the resistance is
1.673 micro ohm cm * 500 cm/0.126 cm^2 = about 2 ohms...
Is 2 ohms important, loss wise?
Using CV^2 = LI^2 and some plausible numbers, I get a few hundred
amps as the peak current.
Perhaps a better way to look at it is to compare the 2 ohms to the
reactance of the primary at the resonant frequency = L*2*pi*f = 104 ohms...
This implies a loss of a few percent.