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Re: [TCML] still stuck at 36
Hi Bart,
Full energy transfer occurs at the first notch. So if you quench at
the first
notch, that's the ideal time to quench. If it takes 6 half cycles to
do a full
energy transfer, then the first notch will be at the 6 half cycle
point. I'm
saying that the gap will never quench at the 3rd half cycle which would
be at a point well before the first notch. I'm saying the coil will
never
quench before the 1st notch, unless a ground stike happens maybe,
but that's a special case. Usually small coils quench at the 3rd notch
or so. This 3rd notch is not before the 1st notch, it's well after that
time. Now let's look at how many half cycles occur by the 4rd notch
for a poor quench situation.
If there are 6 half cycles to the first notch, then there are 18 half
cycles to
the 2nd notch, and 30 half cycles to the 3rd notch, and 42 half cycles
to
the 4th notch. Now if the coil runs at 100kHz, then each half cycle is
5uS. Now assume a poor quench at 4th notch. 5uS x 42 half cycles
= 210uS. This is a considerably longer duration than the 30uS duration
to the 1st notch.
In the example you gave of the 50hHz coil, it's true the full energy
transfer would occur in 63uS. But why do you think the gap would
quench at that time or earlier if it's a poor quenching gap. Only
the best gap might possibly quench at that 63uS which is also the
first notc
h. But if that coil has poor quenching, then it wil quench
much later than the time of full energy transfer. When this happens,
some energy comes back from the secondary to the primary and
keeps the gap lighted, then transfers back to the secondary and
keeps making these round trips until the gap finally quenches at
perhaps the 4th notch in a poor quench situation. Now at a
4th notch quench, the spark duration is actually 512uS. If the
cap charges in 20.75mS, then the ratio is 40.53. This is about
2.5% which is considerably larger than the 1% charge time that
you mentioned. And this is the point I was making.
Your analysis assumes 1st notch quench or sooner. I'm saying
the quench never occurs before the 1st notch. I'm also
saying that in a poor quench situation, the quench will occur
much later than the 1st notch (perhaps the 4th notch).
Now with a smaller coil that runs at 100kHz, and 300bps,
and assuming the same charge time you mentioned, then
the ratio is 81.06 which is still more than the 1% figure you
mentioned. I agree that the cap charging issue is not a large
factor with the poor quench. Since we want to get the
details right, I wrote this to give the correct math and show
the way to calculate the durations to these various quenching
notch-points (3rd notch, 4th notch, or whatever)
Cheers,
John
--
-----Original Message-----
From: bartb <bartb@xxxxxxxxxxxxxxxx>
To: Tesla Coil=2
0Mailing List <tesla@xxxxxxxxxx>
Sent: Wed, 28 Jan 2009 10:24 pm
Subject: Re: [TCML] still stuck at 36
Hi John,
When I mentioned quenching "early", I should have "detailed" my
meaning. I was describing early as "before the full transfer time
expires", not that one would actually quench "early". Quenching early
should always have meaning as quenching prior to the maximum number of
cycles for 1 complete "full" energy transfer. If we have 6 half cycles
for full energy transfer and we quench on the 2nd primary notch (3rd
half cycle), we quenched early (meaning not all the energy in the cap
was transferred before the gap stopped conducting). I believe in most
cases (not all), the gap will usually quench when nearly all the energy
is transferred (should average typically 3rd notch due to the norm of
coil sizes and coupling).
Regarding lower RF frequency coils. Say a 50kHz coil using 10kva pig
and large 200nF cap (big coil, low Fr, powerful). Total energy transfer
time is 63us. At 300 bps on a rotary gap (will need a rotary for this
large coil), charge time would be 20.75ms. This is a ratio of 329 which
is still very large (1% range for transfer time affect on charge time).
But if we assume a very small C (say 20nF) used with this large low RF
coil, then 69us transfer time and 2.075ms charge time under the same
conditions. This ratio is 30. At this point, yes, t
hen it becomes an
issue and starts to eat away at charge time. But this is an extreme and
not the normal coil. However, if any coil was extremely underpowered
and/or really high bps, all bets are off (low RF or not).
In any event, I agree with your summary. Just as Bill has found that a
change in the gap has increased his spark length, I think all of us who
have been down this road have found the same. The greatest improvement
to spark length I personally can attribute to, has always been spark
gap efficiency. Processing power across the gap with minimum losses is
the goal for a performing coil. Bill's coil is yet again another proof
of this.
Take care,
Bart
futuret@xxxxxxx wrote:
Hi Bart,
You're correct that the details are important.
At lower RF frequencies, and if the coil quenches on for example the
5th notch, and if the break rate is lets say 300 bps, the 1000x
situation
won't hold. The total time the gap is lit during one bang could be
200uS. And if the cap has 3000uS to charge between each bang
then it's a 15X ratio which is somewhat significant. But quench time
is not a huge factor, that's why I said the quenching only needs to
be adequate (not excellent).
What often occurs if there's not enough airflow is that the gaps
will run hot. T
his will cause the gaps to fire at a lower voltage and
greatly reduce the bang size, and increase the break rate. This
greatly reduces the spark length. This factor is what hurts the
spark length the most; the reduced firing voltage when the gaps
heat up. And if the gaps heat even more, then true 60Hz power
arcing can occur which completely or partially prevents the cap
from charging.
Regarding the early quench scenario... it never happens. It's >
impossible.
If the gap fires, the best it will quench at is first notch (never >
sooner),
due to air flow. When there's too much air flow, the gap won't quench
early,
instead it will simply fail to fire at times. This is a point that is
often misunderstood.
I agree that the gap resistances don't increase the transfer time
very > much,
and are not a large
factor in gap losses. Gap losses are more due to having
multi-gaps.
I go back to what I said that a single gap has less losses than a
multi-gap, but a single gap is harder to quench and harder to keep
cool, so it needs more airflow.
To summarize again:
1) Poor quenching can reduce the time available for cap charging,
but is a minor factor. Also I believe it's mostly the first transfer
energy that
dete
rmines the spark length, with subsequent transfers contributing
little or nothing to the spark length.
2) Hot running gaps will fire at a lower voltage and give a smaller
bang size which reduces the spark length. This is a very large
factor. (need more air flow)
3) Even hotter gaps will power arc and prevent cap charging and
kill the spark length severely. (need more air flow)
3) Too much air does not cause a too-early quenching. Too-early
quenching is impossible. Instead too much air prevents gap firing
at times. (need less air flow)
4) Multi-gaps have higher losses and give shorter sparks, but
quench more easily, and run cooler with less air needed.
So there are a number of issues to consider. But it's a logical
progression to first select a low-loss gap (single gap), then
cool it with air because single gaps run hot and may have
trouble quenching or may start firing at a lower voltage if
too hot. Also make sure there isn't so much air that the
firing
is interupted at times. A steady firing is needed.
There's no need to worry about quenching too soon,
that can't happen.
John
-----Original Message-----
From: bartb <bartb@xxxxxxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>0
Sent: Tue, 27 Jan 2009 8:44 pm
Subject: Re: [TCML] still stuck at 36
Hi John, > > The single gap with low loss sounds reasonable. The idea
of quenching > sluggishly, well, some variation is possible, but the
consequence is > not a cap charge issue. The charge time on a typical
coil versus the > maximum energy transfer time is over 1000x. For my
4.5"D coil, a 12/60 > NST charging a .0188uF cap, charge time is 18.8ms
for 120bps operation > versus a 17.16us for complete energy transfer
(3.9 cycles at 230kHz). > If we quench slowly, the cap has all day to
charge since the 17us > makes little difference (0.01% of charge time).
> > A quench variation entails a quenching early scenario which would >
leave a charge on the cap (and energy in the cap). The cap would then >
charge to breakdown more quickly to the next due to the charge left on
> the cap (the line between A and B just got shorter, bps increases, >
spark length diminishes). But this also states that all the energy in >
the cap did not make it through the transfer (this is why spark length
> decreases and not so much the bps which was simply a result). I think
nearly all of the energy transfers, an
d so much so, that the voltage left on the cap is insignificant in
the > same fashion as the ratio between cap charge time and energy
transfer > time, and more so in a
static voltage clamping gap as
opposed to a > rotary. > > Energy transfer time does make a difference
of course (energy and > time). But the gap cannot affect the energy
transfer time > significantly by quenching early (but it can by
preventing extensions > of the transfer time in an extremely bad
situation). This would be due > to gap impedance. > > Energy transfer
time is based on the mutual inductance and frequency. > For my 4.5"D
coil, reactance as based off of the mutual inductance is > 123 ohms. If
the gap was ridiculously lossy, it's resistance would add > to this
reactance. In a completely theoretical case where the gap > resistance
was equal to this reactance, the transfer time would be > double. It is
still insignificant regarding cap charge time. However, > the em force
enveloping the secondary would certainly be reduced (time > and
energy), and this would affect energy stored in the top load. > > But
now for the gotcha! Gap resistances are less than 1 ohm. So gap >
losses are not affecting energy transfer times. I think it's all about
> simple power losses at the gap that are the real cause of pain and >
suffering with spark lengths which is why significant air cooling >
drastically improves any static gap style (some styles are better than
0D
others at accomplishing this). There is always the issue of too high
a > velocity at the breakdown point that blows out the
spark. This is a
> quenching early issue, which of course doesn't transfer "all" the >
energy in the cap and thus we see spark lengths diminish and bps rise.
> This is why some find using a variac on the air voltage is not always
> best at 100%. > > Hope I'm making sense. Sorry for being long winded,
but it's one of > those "devil in the details" subjects. > Best
Regards, > Bart > > futuret@xxxxxxx wrote: >> I think what makes a
hyperbaric gap perform well is that it's >> a single gap. This makes it
a low loss gap. Once you have a >> low loss gap then all that's needed
is to quench it adequately. >> Since a single gap is harder to quench
than a multi-gap, this >> is why a good amount of air flow is needed.
>> >> The air flow is >> also needed to cool the electrodes. If there's
not enough >> air flow the gaps may run too hot and may begin to power
arc, >> or quench very sluggishly. If a gap quenches too slowly, >>
then less time is available to recharge the capacitor and >> output
suffers. >> >> If there's too much air, then >> the gap may fire
intermittently with a sort of stuttering >> action and this cuts the
spark length too. It's not really >> over-quenching, it's simply
erratic firing=2
0in the first place. >> It's not that the gap quenches too fast,
rather it's that >> the gap does not fire consistently. >> >> John >>
-- > >> >> -
----Original Message----- >> From: DC Cox
<resonance@xxxxxxxxxxxx> >> To: Tesla Coil Mailing List
<tesla@xxxxxxxxxx> >> Sent: Tue, 27 Jan 2009 4:58 pm >> Subject: Re:
[TCML] still stuck at 36 >> >> >> >> It's not clear why to me either.
My best guess is better cooling due >> to the >> high velocity air, and
perhaps increased turbulence >> around the ends of the copper pipes. >>
>> I know that most coils performance jumps in amazing quantity of
spark >> output >> when the hyperbaric gap is used. I have never used
it above 4 kVA as > a >> single gap, but did some experiments at 7 kVA
with a dual series > > hyperbaric >> gap and it seemed to work as good
as a small rotary. >> >> Perhaps looking at scope ringdowns with and
without a hyperbaric gap >> might >> provide some clues. >> >> Dr.
Resonance >> >> >> >> >> On Tue, Jan 27, 2009 at 1:51 PM, Lau, Gary
<Gary.Lau@xxxxxx> wrote: >> >>> I don't disagree that hyperbaric gaps
work well, but I'd like to be >> clear >>> on why. Too often on this
List, the word "quenching" is used > > incorrectly. >>> My measurements
showed conclusively that hype
rbaric gap losses were
lower >>> than in a sucker gap, but I made no attempt to measure
actual > > quenching. >>> Quenching is unrelated to gap losses and
refers to how many pri-sec >> energy >>> trades occur before the gap
extinguishes. In fact, I think that > > typically,
>>> lossy gaps (at
least multi-segment gaps) have superior quenching. >>> >>> So, have you
seen evidence that actual quenching, as observed on a > > scope, >>>
was superior with the hyperbaric gap? Was this with free-air > >
streamers or >>> grounded (connected) streamers? Seems like a very
difficult thing to >>> accurately compare between two systems. >>> >>>
Regards, Gary Lau >>> MA, USA >>> >>> > -----Original Message----- >>>
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] > On
>>> > Behalf Of DC Cox >>> > Sent: Tuesday, January 27, 2009 1:31 PM
>>> > To: Tesla Coil Mailing List >>> > Subject: Re: [TCML] still stuck
at 36 >>> > >>> > Bill: >>> > >>> > What was your maximum spark before
you used the hyperbaric > sparkgap? >>> > >>> > Also, put a variac on
the vac. cleaner motor, and fine adjustment >> of the >>> > speed will
increase your output even more. Usually best output >>> > around 75% of
the variac. >>> > >>> > I know they work great. They always increase
your sec spark output >>> 20> dramatically which means we have been
underquenching >>> > with most of our previous designs. >>> > >>> > Dr.
Resonance >>> > >>> > >>> > >>> > >>> > On Tue, Jan 27, 2009 at 5:50
AM, Bill Bohn <b.jbohn@xxxxxxxxxxx> > > wrote: >>> > >>> > > I built
the hyperbaric gap as described WOW!Now I get 44" I am > > using a >>>
shop >>> > > vac for suction.I am using205 of the 6 strings of caps.I
think I >> did >>> some >>> > > damage >>> > > >>> > > To my 5-1/4
coil.Now I have a 6.625" secondary wound 26.5" 1060 >> turns. >>> Top
>>> > > load is 4.5x18 toroid and a 7" sphere.Seems best with the >
primary >>> clamped >>> > > >>> > > At turn 5.The spark sounds somewhat
eratic and choppy.IT will > > smooth >>> out >>> > > some by adjusting
the spark gap closer at the loss of streamer > > length . >>> > > >>> >
> What is the method of measuring BPS?IT doesn't seem to sound > >
right.The >>> > > coupling between primary and secondary is 0.I am
going to put > the > 6 >>> strings >>> > > of >>> > > >>> > > My mmc
cap in but I think it will be best tuned at about turn 2 >> and >>>
become >>> > > even more erratic. >>> > > >>> > > I am getting positive
results and thank everyone for all the > > ideas20and >>> 2 >>> > >
cents worth. >>> > > >>> > >
_______________________________________________ >>> > > Tesla mailing
list >>> > > Tesla@xxxxxxxxxxxxxx >>> > >
http://www.pupman.com/mailman/listinfo/tesla >>> > > >>> >
_______________________________________________ >>> > Tesla mailing
list >>> > Tesla@xxxxxxxxxxxxxx >>> >
http://www.pupman.com/mailman/listinfo/tesla >>>
_______________________________________________ >>> Tesla mailing list
>>> Tesla@xxxxxxxxxxxxxx >>>
http://www.pupman.com/mailman/listinfo/tesla >>> >>
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