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Re: [TCML] Toroid Problems



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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