[TCML] Spark gap Resistance
resonance at wildblue.net
Tue Nov 20 11:46:23 MST 2007
John has hit on a very important point here. With classic RSG type coils
2nd thru 4th notch quenching seems to work best. As he suggested the
problem lies in deionization or interruption of the spark gap. This is
problamatic due to the very high temperatures involved in the spark channel,
especially with all the capacitive energy behind it.
This is one reason why experimenters are now turning to the dual resonant
solid state coil drivers to replace the less efficient spark gap type
switches. The IGBT type switches, replacing the open air spark gaps, are
able to turn on and off at higher rates providing more rapid dI/dt rates.
Due to the fact there is no open air spark, excessive heat does not provide
the shut-off conductive problems that a spark gap endures.
The switching off part is much more efficient, less heat and no light energy
is wasted, and the IGBT type switching allows the experimenter to keep 30%
more energy in the secondary coil to ring up without trying to dump the
energy back into the primary system. First notch quenching is achieved with
efficiency. Spark lengths are exceeding the classic 1 ft per kVA range
typical with RSG systems.
For this same reason, classic type coils like a coeff. of coupling in the
range of 0.18 to 0.14 while solid state coils, with much more rapid
switch-off characteristics, operate in the coeff. of coupling range of 0.16
to 0.20. At present, research suggests that 0.18 is usually a very
efficient design goal for max power transfer. Smaller coil systems can
tolerate up to 0.20 while larger coils seem to operate best around 0.18.
Bart Andersons excellent computer design program, JAVATC, allows one to
experiment with different sec heights and primary inner and outer radii to
obtain the desired coeff. of coupling range. It's easy to use and very
accurate. It works great with both classic RSG coil designs and dual
resonant solid state coil designs. Just note the different design goals for
the coeff. of coupling as you adjust your inner and outer primary radii and
also the height of the sec lower winding above the primary. I usually use
0.25 inch elevation of the sec above the horizontal plane of the primary for
high coupling. Pri-sec spacing usually around 0.5 inch.
Use as large of a dia secondary coil as practical, typically around 10 to 20
inch dia range, to obtain max. sec potential. This also helps keep the res
freq low while helps the IGBTs switch more efficiently. They are rated at
75 kHz, but operate more efficiently below 50 kHz.
Experimenters who have seen a solid state coil in action immediately notice
the very loud "mean sound" from the spark as the much higher currents tears
the air molecules apart in the spark discharge. The spark is also white hot
and not blue or purple like the lower secondary coil currents in a classic
RSG design. Keeping the energy in the secondary coil is the name of the
game for maximum performance.
Many happy Holiday sparks!
Resonance Research Corp.
----- Original Message -----
From: <FutureT at aol.com>
To: <tesla at pupman.com>
Sent: Monday, November 19, 2007 9:13 PM
Subject: Re: [TCML] Spark gap Resistance
> In a message dated 11/19/2007 10:14:29 P.M. US Eastern Standard Time,
> bartb at classictesla.com writes:
> I think Chris brings up a "very" valid point! The problem is, it is
> experience that drives the idea of a higher surge impedance. There's a
> reason it's termed "surge" impedance. There is a difficulty at quenching
> after the first notch. Those who have done this have reported in the
> past (from my memory) that they had better sparks lengths on 2nd or 3rd
> notch quenching as compared to 1st notch quenching.
> Those experiments which obtained 1st notch quenching did so by increasing
> losses by using multiple gaps. It was a bad trade off. I think the
> it's better to let a coil quench at 2nd or 3rd notch if it "wants" to, is
> most of the spark growth occurs during the first transfer. So the extra
> (during a single bang)
> don't do much except waste some power and steal some cap charging time.
> If one forces the 1st notch quenching by using lossy gaps, then even that
> important transfer is weakened. This reduces the spark length. There is
> evidence that large powerful coils more easily quench on the first notch.
> For example Ed Wingate's magnifier quenches on the first notch at full
> But at low power I think it quenches on the 3rd notch. I seem to
> that the "effective" coupling for his magnifier is about k = 0.2 maybe
> It's more
> or less the same as a classic coil. The 12 point series rotary may be
> the quenching. It would be interesting to monitor the quenching using a
> typical 4 point series rotary. In any case the lower frequency of a
> makes the notches wider, so it's easier for the ions to de-ionize during
> and let the gap quench.
> Chris, several years ago, 1st notch quenching was the assumed ideal and
> we tried to do that for all the reason's you stated. What was found is
> that 1st notch quenching was not easy. Then, we found that when it
> occurred, it wasn't "wonderful". How could that be? Well, losses of
> Chris is trying to quench faster by using a fast rotary. That won't
> because the quench is not controlled by the mechanical dwell time.
> The spark at the gap will arc before the electrodes line up, and stretch
> out if needed after the electrodes pull apart. To really stretch the
> and force the quench would require a rotary gap construction well beyond
> what anyone has tried. Generally rotaries are more for timing when the
> spark occurs rather than for quenching purposes. Quenching is more
> about draining the energy out of the system quickly. For the most part,
> air streamers don't drain the energy that quickly, and that's the main
> problem preventing a fast quench. In any case, as you said Bart, a fast
> quench is not really very important. It's interesting to consider the
> various DRSSTC designs and SISG coils which have lower switching
> losses. They may be more efficient because of that, but the improvement
> is not huge compared to a spark gap coil. This shows that the gap losses
> (at least the part of the gap losses that matter) are not that large.
> It's difficult to figure out and in my mind, it's still "not" figured
> out. We do know that when the surge impedance is increased due to higher
> inductance, we can get better spark output. But, there of course is a
> limit. It is counter-intuitive to physics when all the pieces of the
> puzzle are not accounted for. The only way "I" personally can explain it
> is that the losses incurred during energy transfer in a single notch
> arena are huge.
> If the single notch quenching is "forced" by deliberately increasing the
> gap losses, then yes the gap losses will be high. It's best not to do
> It's best to accept a 2nd or 3rd notch quench, but keep the gap losses as
> low as possible.
> Forcing the quench in that way is really just wasting the energy in the
> gap so there's mostly none left by the time the 1st notch arrives.
> Now, are those losses in the gap?
> If first notch quench is forced by using a lossy gap, then yes the losses
> are in the gap. But in all coils the losses are shared between the gap,
> the primary and the secondary, in some proportion.
> Are they also shared
> in the secondary or primary to a large degree? The question is "where
> are the losses and what is their distribution" in this 1st notch quench
> Again, if 1st notch quench is forced by making a lossy gap, then
> the extra losses are in the gap, or mostly in the gap. If however the
> quench could be forced
> by an air blast or magnetic field or something similar, then there would
> be a benefit because the caps would have more time to charge. But
> the spark might not get longer, because energy is not being
> transferred faster. We can transfer the energy faster by increasing the
> coupling, but then the sparks won't be able to drain out the energy
> fast enough. It will again become more difficult to quench on the 1st
> and an even stronger air blast or magnets, etc., will be needed.
> The reason that tighter coupling increases spark lengths is because
> the energy is transferred faster, before too much of it is wasted in gap
> It's all a matter of getting as much energy to the secondary during the
> first transfer as far as I can tell. This energy will produce the spark
> then if some energy reflects back to the primary, the spark length has
> been produced.
> Were talking about high energy pulse currents. If there is an escape
> route, high energy pulse currents will find it.
> It seems to me that what we are doing is increasing energy transfer time
> to a degree in which the secondary and spark gap can "handle" the energy
> as a combined system. I believe that when we attain first notch
> quenching, we are simply releasing energy that is not being accounted
> for. It's not getting to the sparks, so it's a loss somewhere else.
> Yes, when the quench is forced by building a lossy gap, then the gap
> more energy. Since the energy is now used up more quickly, it lets the
> gap quench more quickly. But if first notch quenching can be obtained
> by using air blasts or something similar but without making the gap
> lossy, (and without reducing the coupling) then a benefit may be seen.
> Reducing the coupling has a similar effect on spark length, as using a
> lossy gap. Both waste energy before it can get to the secondary.
> Take care,
> FutureT at aol.com wrote:
>> In a message dated 11/19/2007 6:54:37 P.M. US Eastern Standard Time,
>> list at future-technologies.co.uk writes:
>> If the current is less overall, then the gap losses are lower. Using a
>> primary results in less overall current and less overall losses. When
>> (more turns) are used in the primary, the inductance increases more than
>> resistance increases, thus the primary losses are reduced. The Q is
>> The result is that
>> both the gap losses and the primary losses are reduced. Of course this
>> works up to a point. At some point the secondary wire will be too
>> thin and will show high losses.
>> Generally low frequencies are believed to be more efficient in
>> long sparks.
>> Maybe something in the range of 30kHz to 150hHz. Also at higher
>> it's harder to achieve a first notch quench. The sparks themselves may
>> better at low frequencies.
>> Large coils are generally more efficient than small ones.
>> Tank caps generally are able to provide their current fast enough for
>> TC operations.
>> Generally high breakrate coils need more input power to produce a
>> spark length. It's not known exactly what breakrate is best. It may
>> somewhat among coils. Somewhere between 100bps to 200bps usually
>> works well.
>>> Sorry for the amount of "ponders" in this mail. It is just my
>>> that a higher frequency with less primary turns and a faster RSG
>>> overall reduce losses far more than anything else.
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