Re: [TCML] SSTC full bridge control system question

[Steve Ward <steve.ward@xxxxxxxxx>]

Mike, the phase reversal is in the *secondary* current with respect to the
primary current, which when you consider the mutual inductance, causes a
large cancellation of primary current (can be nearly 100%).  Choosing the
ratios per Antonio's math is just sort of another way of specifying tuning
and coupling coefficient (as far as i can tell).  The sad thing is that
while mathematically elegant and nice, it does fall apart a bit when
streamer loading comes into play.  And as far as i know, no one has a
streamer model that includes the dynamic effects that truly determine the
streamer impedance.  Its certainly not an easy problem either, any of my
measurements suggest the streamer impedance really jumps around a lot
depending on whats out there for your spark.

Steve

On Mon, May 3, 2010 at 7:22 AM, Michael Twieg <mdt24@xxxxxxxx> wrote:

> That was a fascinating read Antonio.  I was able to replicate your
> results accurately, even in my zero-crossing control model.  I didn't
> think that complete beating in the signals was possible with
> zero-crossing switching, since the beating should require a reversal
> of phase.  In my previous simulations, the system was always excited
> to the primary resonant frequencies, and never the "middle" frequency
> as in you explanation.  Would this be because my own attempts didn't
> meat your criteria for the spacings/ratios between the resonant and
> middle frequencies?  I'm still a little cloudy on what you mean by
> "odd" and "double odd" differences.
>
> Many thanks,
> -Mike
>
> On Sun, May 2, 2010 at 4:40 PM, Antonio Carlos M. de Queiroz
> <acmdq@xxxxxxxxxx> wrote:
> > Michael Twieg wrote:
> >>
> >> Hello, this is my first post, please be kind,
> >> I'm working with a team of engineers to build a large solid state
> musical
> >> tesla coil, and my task in to project is to build control and telemetry
> >> hardware.  We've chosen a full bridge design, a two coil configuration
> >> (flat
> >> spiral primary), and we're using an interrupter based loosely on steve
> >> ward's design to control its switching.  Like his, it senses primary
> >> current
> >> and switches on zero crossing.  I've built the hardware and verified
> that
> >> it
> >> works in small scale testing...
> >
> > As Steve already said, the best tuning is the one that produces complete,
> or
> > almost complete notches
> > in the primary current (and capacitor voltage). At the notches all the
> > energy in the system is in the
> > secondary capacitance. This tuning is achieved, ignoring streamer
> loading,
> > with a tuning exactly between
> > the two resonances, if the system is designed for this. It is possible to
> > obtain greater secondary voltage,
> > but at the expense of much higher input current, as you probably noticed.
> If
> > you have a certain
> > maximum input current and a given load capacitance, the system can always
> be
> > designed to operate in
> > this "notched" way making optimum use of the current and with natural
> zero
> > current switching. I have
> > more detalis about this here:
> > http://www.coe.ufrj.br/~acmq/tesla/drsstc.html<http://www.coe.ufrj.br/%7Eacmq/tesla/drsstc.html>
> >
> > Antonio Carlos M. de Queiroz
> >
> > _______________________________________________
> > Tesla mailing list
> > Tesla@xxxxxxxxxx
> > http://www.pupman.com/mailman/listinfo/tesla
> >
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