RE: twin coil transmission lines (fwd)

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---------- Forwarded message ----------
Date: Wed, 30 May 2007 17:44:13 -0400
From: "Lau, Gary" <Gary.Lau@xxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: RE: twin coil transmission lines (fwd)

Hi Jim:

Is it really correct to compare the skin-effect resistive losses of the
transmission line, to the primary reactance, to reach an incremental
loss percentage?  The primary reactance isn't a loss at all.  

In contrast, the AC resistance of various primary coils that I tested
(http://www.laushaus.com/tesla/primary_resistance.htm) were 0.18 to 0.39
Ohms for a 67uH primary at 100KHz.  So if the transmission line really
did add 2 Ohms, I believe that would be significant.

Regards, Gary Lau
MA, USA


> 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>
> >To: tesla@xxxxxxxxxx
> >Cc: drieben@xxxxxxxxxxx
> >Subject: twin coil transmission lines
> >
> >Hi all,
> >
> >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.
> 
> 
> 
> 
>