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Re: 2 questions on resonance

Tesla List wrote:
> 
> Original Poster: Terry Fritz <twf-at-verinet-dot-com>
> 
> Hi Gary,
> 
> At 10:17 AM 4/7/99 -0400, you wrote:
> >>Original Poster: "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
> >>
> >>Dear all,
> >>          After reading the responses on resonant rise, I would like
> >>to ask why it is said that resonant charging allows one to suck more
> >>power from a NST? I suggest that if that were true, one could set the
> >>gap wider than for a non-resonant situation and still have the gap
> >>fire at the 2Fmains rate. Any comments?
> >>
> >>Malcolm
> >
> >Good question.  I have always assumed this to be the case too.
> >Certainly if allowed to build over multiple cycles, the resulting voltage
> >will be highest when resonance is met, but I just ran some quick
> >simulations with differing capacitances and a 15KV/60mA NST and see some
> >surprising things that now make me question this "wisdom".
> >
> >As expected, if allowed to run over multiple cycles, highest peak voltage
> >occurs with a 10.8nF cap (which is precisely mains-resonant at 60Hz).
> >But allowing the gap not to fire over multiple half-cycles is something
> >that should never be allowed to occur, and therefore is irrelevant.
> >
> >Now, if I assume the gap is sized to fire exactly once per half-cycle (as
> >if a sync RSG or precisely gauged static gap were used) and only look at
> >the peak cap voltage after the first half-cycle, it gets interesting.
> >The highest cap voltage did not occur with the 10.8nF cap, but with one
> >something less than 4nF.  But this is not the whole story either.
> >Highest POWER occurs with highest (1/2 CV**2), assuming a constant gap
> >firing rate.  The highest POWER occured with between 25-30nF.
> 
> Neat isn't it!  It is no coencidence that my cap is now 27.5nF on my 15kV
60mA
> neon.  I have not been able to pursue much actual testing of this
confuguration
> due to problems finding time but it DOES work fine in real life.  As far as I
> know, this is the best configuration to pull power out of a single neon.  An
> added benifit is that the voltages and currents from the transformer are only
a
> tiny bit over the transformer's ratings so nother should burn out.  The model
> seems to be very acurately predicting the real life behavior of using this
very
> large cap value.
> 
> >
> >These numbers are a rough first pass, because I did not optimize the
> >phase of the gap firing to be consistent every mains half-cycle, as would
> >be the case if using a sync RSG.  Terry has pointed out that if one does
> >use a sync RSG, the optimum cap is 17-20nF, and this does take into
> >account adjusting the phase for consistent firing every half-cycle.  I
> >see this also if I tweak the simulation phase (somewhat tedious).
> 
> My new dual 400MHZ Pentium II helped me with the tweaking here :-))  Trial
and
> error is the best way I know of to find the best phase dealy value.  Of
course,
> in actual life, the phase just finds the best place all by itself which
agrees
> well with what the model shows.
> 
> >
> >It will be interesting to run a similar simulation with the gap firing
> >multiple times per half-cycle, to see which cap size draws highest power.
> >Using static gaps, this is a more realistic scenario, as the voltages
> >seem to get out of hand if you only allow one big bang per half cycle.  It
> >also looks like when using sync RSG's, the caps had better be rated for a
> >higher voltage than with a static gap configuration, particularly when
> >using lower capacitance values.
> 
> In my modeling, the other smaller cap values always deliver less power to the
> arc...
> 
> >
> >Until then, I don't see any evidence of higher power being pulled through
> >the use of resonant charging.  Thank you Malcolm, for bringing this up.
> 
>         I think the 27.5nF cap size is delivering the highest power I have
seen
> out of a single 60mA neon so far.  There is some thought that more than
120BPS
> "feeds" the streamers better but for maxium power to the arc, the 27.5nF cap
> configuration is the best I have seen.
> 
>         I don't really think the resonant charging mode is doing the best
job.
> The 27.5nF case seems to do much better for me.  Perhaps you will convince
> yourself of this too and I woun't be all alone in my beleif that the highest
> power transfer point is far away from the resonanat charging point for cap
> values.  It is also much safe the the cap and neon...
> 
> Cheers,
> 
>         Terry
> 
> >
> >Gary Lau
> >Waltham, MA USA

Terry:

        Have you observed chaotic behavior during you simulations?  I have a
file of simulated waveforms I've been intending to post for over a year,
but have never bothered to annotation them so they would make sense to
anyone.  They appear to duplicate at least part of your study.

Ed