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Re: Inductive Kick Effects - was- Re: cap firing voltage scopemeasurements q...
In a message dated 99-06-19 04:10:28 EDT, you write:
<<
> Hi John, Malcolm, Richie, All,
> Well, I finally get it too! Richie sent me an excellent model that
made
> the effect simple enough for me to understand too :-)) Basically, the gap
> switching is changing the system from a resonant charging circuit to more
> of an inductive kick charging circuit. It is storing energy in the
> inductor and then the switching action allows a sudden high voltage kick
> right after the gap opens that charges the cap up to a higher voltage than
> the circuit would normally produce.
Malcolm, Richie, all,
I never considered this either, but it certainly makes sense. It looks
like we have to be more concerned about the LTR arrangements overvolting
things, than the reso-caps. I noticed that my sync gap is firing about
60 degrees past the peak. I haven't yet done a comparison to see
what firing position gives the strongest inductive kick voltage rise,
maybe the simulations show this? In my system, when the voltage
dips lower just after firing, it reaches a level that is about 1/4 the
(absolute value) level that is ultimately reached at the opposite
polarity. I suppose this effect might occur at 240bps or higher also,
to some degree? More below.
>This works much like those power
> supply ICs that switch current across an inductor to get -15 volts from +5
> volts input.
> The real key is the energy that is stored in the inductor when that
gap
> fires. I made this table of stored energy in my new LTR coil just before
> the gap fires.
> Neon Primary 24.95 J
> Neon Secondary 23.75 J
> Filter Caps 0.2 J
> Primary Cap 5.97 J
> Primary Inductor 0.0J
> Obviously, the neon transformer is storing an overwhelming amount of
> energy. At only 80 mA across each of it's giant 3700H inductances, a
> secondary winding stores 1/2 x L x I^2 = 11.84 Joules per side!! I never
> considered this before. The computer programs just crunched this factor
> with everything else but I was oblivious to this giant energy being stored.
> The neon is acting much like a current source do to the giant inductance
> and will push current into the cap as it pleases causing the cap voltage to
> skyrocket!! It is possible to get up to 100+ kV if one really tries! Of
> course, the smaller the primary cap, the more voltage the inductor will
> push it to...
> This is apparently the mechanism behind the LTR coil's ability to
charge
> larger cap values than one would normally expect. I knew from computer
> simulations that the effect was there but I never really understood why
> before. *:-)
Can static gaps be set to such a spacing that this effect will occur?
This might explain why Gary got good results with static gaps and
LTR's, and I generally didn't. I'll have to look at that again.
> Consider this; If a cap were charged continuously at a rate of 60mA,
what
> value cap could one charge if the end voltage were 21.2kV? V = 1/C x I x T
> so 20000 = 1/C x 0.06 x 1/120. C=23.6nF which is just what an LTR coil
> with a 60mA neon likes to run! Perhaps this is a governing equation for
> LTR coils given and available RMS current level? Perhaps this can be used
> to very easily calculate what size cap a give power transformer will
> ideally charge?
Very interesting, I'll have to look this over some more.
> Many thanks to Richie for helping me to see all this!! This whole LTR
> things just became much more clear but now has added factors to consider...
Thanks guys, definitely an interesting development.
John Freau
> Terry >>