Thanks for the info, Wil!
On Wed, Oct 1, 2014 at 6:58 PM, William Howard <snakeprior@xxxxxxxxx> wrote:
> Atomic,
> You can use a parallel LC network but you loose control over the
> oscillations inside the tank. I don't think audio modulation would work.
> Plus you would need to limit the inrush current as it will look like a
> short circuit to your switch.
>
> A VTTC uses a parallel LC network but runs constant wave. A car with a
> ignition coil uses a parallel LC network as there is a capacitor in
> parallel with the ignition coil. This produces a transient AC wave.
>
> I conducted an experiment a few years ago where I used a relay to dump a
> charged 450v electrolytic into a ignition coil with a capacitor in parallel
> with the primary. The sparks resembled a Tesla Coil (with branches and
> leaves). The frequency was too low to produce a air discharge tho.
>
> I don't know many other applications of a pulsed system that uses a
> parallel LC network.
>
> Tesla described this setup in his Colorado notes in July.
>
> http://www.bibliotecapleyades.net/tesla/coloradonotes/coloradonotes03.htm#Colorado
> Springs Notes - July 1-31, 1899
>
> He stated " It secures two chief advantages: 1) less current through the
> break and more through the primary and 2) longer and better oscillation in
> circuit including primary because it is easy to constitute such a system
> without break with an extremely small resistance or frictional waste.".
>
> He had the switch and tank cap in the opposite place to mine however. But I
> don't think it would matter much.
>
> For a system like this your only dumping the capacitors energy into a tuned
> LC network. So while a faster switch time will help it's probably not that
> crucial and your tank circuit can be as high or low as you want in
> frequency.
>
> That's why I think a SCR would work as it would only need to conduct 1 to
> 1000 times per second. Also it's not switching tank currents so reverse
> voltage shouldn't be a problem and the energy switched will be reduced.
> Also timing will also be less crucial as long as the coil has rung out
> before the next pulse. I know next to nothing about IGBTs and other
> semiconductors.
>
> Keep in mind I've only made 10cm streamers so far with a thyratron. I need
> to do a lot more work to get close to a decent system.
>
> Also keep in mind I am a layman. I will defer to the experts on this group.
>
> Cheers!
> -Wil
> On 02/10/2014 3:49 AM, "Atomic" <atomicrox@xxxxxxxxx> wrote:
>
> > This is a very interesting idea, I didn't know you could just parallel
> the
> > tank capacitor and primary like that.
> >
> > From what I understood the thyratron is working only as an interrupter.
> > Excuse my ignorance, but wouldn't that make it possible to make a much
> > simpler DRSSTC that uses a single IGBT/MOSFET in place of that thyratron?
> > If it works that'd avoid most of the hassle in setting up/building a
> > DRSSTC, and would still have the sound modulation and "traditional"
> > streamers.
> >
> > On Mon, Sep 29, 2014 at 10:13 AM, William Howard <snakeprior@xxxxxxxxx>
> > wrote:
> >
> > > Dear Group,
> > > I was dredging through the list archives and found mention of SCRs
> being
> > > successfully used by a man in a magnifier years ago.
> > >
> > > I found his website in the archives but it only has two pages:
> > >
> > >
> >
> https://web.archive.org/web/20010519065013/http://home.hiwaay.net/~eburwell/
> > >
> > > I am continuing my work with thyratron pumped tesla coils and had the
> > idea
> > > of using an inductor to limit current into the parallel LC network (to
> > > reduce stresses on the thyratron and pulse cap). It was good to see he
> > had
> > > already used the idea years ago to limit the current through the SCR.
> > >
> > > I know the conduction time and recovery is longer for a SCR than a H2
> > > thyratron but seems as they are not shuffling energy between the
> inductor
> > > and capacitor in the tank circuit it shouldn't matter. There would just
> > be
> > > a variable pulse rate at which the SCR discharges a capacitor into the
> > > parallel tuned LC network. I would be looking at 200 to 2000 pps.
> > >
> > > Here is a schematic of my existing thyratron tesla coil, an SCR just
> need
> > > be substituted:
> > >
> > >
> >
> http://russianpoweredvttc.blogspot.com.au/2014/09/thyratron-tesla-coil-plans-theory-and.html?m=1
> > >
> > > A saturable reactor would need to be added to limit current through the
> > > SCR.
> > >
> > > I find this idea attractive because SSTC are too difficult for me to
> > build
> > > and SCRs are pretty cheap.
> > >
> > > It would be a very simple thing to test. As a layman I have to ask is
> > there
> > > any flaws to this idea?
> > >
> > > Cheers!
> > > -Wil
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