Re: [TCML] Toroid Problems

[Quarkster <quarkster@xxxxxxx>]

Jim -
   
  Good analysis  ..... but the point I was trying to make was that that all the wiring in the tank circuit appeared to be small gage (#16AWG?), but it could also have been #18 or even #20. I was hoping that Nicholas would specify the actual size used, and also look how excess wire length used in the tank circuit connections could affect his calculated primary resonant frequency.
   
  For those few coiler's who are willing to make carefully controlled experiments, and strive to get that last 1/2" of performance out of a coil, a 2% performance gain by lower resistance wiring, a 3% gain in a lower loss spark gap, a 1% gain by making all bolted connections clean and tight, etc, etc. may be worth the effort.
   
  Regards,
  Herr Zapp

jimlux <jimlux@xxxxxxxxxxxxx> wrote:
  Quarkster wrote:
> Nicholas -
> 
> A few areas of concern are revealed by your photos:
> 
> 1. It looks like your tank wiring to the MMC and spark gap is
> extremely small gage stranded wire (#16 AWG?). All the interconnects
> between primary coil, spark gap, and tank capacitor need to be fairly
> heavy gage (I recommend no smaller than #12 AWG for a small NST
> powered coil). The peak current in the tank circuit can be hundreds
> of amps when the spark gap fires and the tank capacitor dumps all of
> its energy, and #16 AWG is not adequate.

This is just not true. The peak current may be relatively high, but 
even so, the losses just aren't that high, compared to the losses in the 
gap itself. Consider that the difference in diameter between AWG 12 and 
16 is about a factor of 1.4. Therefore, the loss goes as the same ratio.

Let's assume for a moment that you have AWG 10 wire (just because it's 
easy to remember the resistance.. 1 mOhm/ft).. Say you have 2 feet.. 
that's 2 mOhm total. Also assume that the peak current is 1000 Amps ( 
if Cpri is 0.1 uF and Lpri is 30 uH, 15kV turns into 866A, assuming NO 
losses anywhere else)

So the voltage drop across that couple feet of wire is 2V.. compare that 
to the 100V or so across the gap.

Now, go to AWG 16, which will have twice the resistance (at DC).. Now 
the drop in the wire is 4V.. Overall the loss has increased by 2/104, or 
about 2%...


Don't go using AWG20.. but the difference between AWG 12 and AWG16



> 
> 2. All the wiring in the tank circuit needs to as short and direct as
> possible. You didn't post any photos of the overall coil and all the
> interconnects, but I suspect that your primary wiring may be longer
> than necessary. It appears that you have carefully calculated the
> inductance and resonant frequency of both primary and secondary
> coils, but I bet you did NOT include the length of the additional
> tank circuit wiring in your primary coil calculations. Measure the
> total length of your primary wiring, include this in the length of
> the primary coil, and re-calculate primary inductance and resonant
> frequency. It may be much lower than you thought. You may need to
> relocate the spark gap and the MMC to keep the primary wiring as
> short and direct as possible.

Figure about 1 uH/meter for wire.. A typical L is 30-50 uH, so a couple 
extra uH will drop the Fres about 3-5 %
> 

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