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Re: SSTC, Class DE High Power Half Wave Inverter Design



Original poster: "David Sharpe by way of Terry Fritz <twftesla-at-qwest-dot-net>" <sccr4us-at-erols-dot-com>

Ken
Are you suggesting that a 170:1 CT feeding a 1T ring as a drive primary may be
any optimum way to feed a resonator?  I have an idea that I've been working
on...

Regards
Dave Sharpe, TCBOR
Chesterfield, VA. USA

Tesla list wrote:

> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Kchdlh-at-aol-dot-com>
>
> In a message dated 01/28/2002 9:52:05 PM Pacific Standard Time,
> tesla-at-pupman-dot-com writes:
>
> >
> > Subj:SSTC, Class DE High Power Half Wave Inverter Design
> > Date:01/28/2002 9:52:05 PM Pacific Standard Time
> > From:<mailto:tesla-at-pupman-dot-com>tesla-at-pupman-dot-com
> > To:<mailto:tesla-at-pupman-dot-com>tesla-at-pupman-dot-com
> > Sent from the Internet
> >
> >
> >
> > Original poster: "David Sharpe by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> > <sccr4us-at-erols-dot-com>
> >
> > All
> >
> > While researching the web for DE inverter designs this article popped
> > out of google (www.google-dot-com)
> >
> > http://www.chipcenter-dot-com/analog/images/tn/tn038.pdf
> >
> > This inverter is scaleable from 50Khz to better then 6Mhz, and has
> > very high efficiencies, and supposedly is relatively resistant to load
> > impedance swings.  Circuits and full design info supplied.  Looks
> > good I've already downloaded it for my SSTC file.  Good stuff...
> >
> > Regards
> > Dave Sharpe, TCBOR
> > Chesterfield, VA. USA
> >
> >
>
> That was a good find!  It's a PhD thesis, of course.  The candidate did an
> excellent job--very thorough design and analysis work, in my opinion.
Although
> his circuit design incorporates the use of a resonant load, I should
think that
> it should quite well drive a non-resonant Tesla coil primary.  In such a
case,
> of course, operation would not be class DE but rather, class D; but at
100 KHz
> or so, not a problem.  And in such a case, one could excite his driving
> circuits with the secondary's return-signal, as I do, thus making the system
> self-tuned.
>
> A more fundamental limitation, for Tesla-coil work, of a half-bridge circuit
> such as this design incorporates, is that the signal voltage that can be
> applied to the primary is limited to what the half-bridge MOSFETs can
> withstand: perhaps 400V for 500V MOSFETs.  That limitation is what I've tried
> to overcome with my "current-loop" design.  In that design, I incorporate,
> presently, 5 MOSFET pairs and 5, 160V power sources in a "daisy chain"
primary
> configuration.  That applies some 800V--less MOSFET drops, of course--of
signal
> to my 4-turn, 12"-dia. primary.  But that is still very much less, it must be
> said, than the punch that can be delivered by a spark gap since that can
> deliver maybe 10x that voltage.
>
> The following has always seemed to me to be important:  1.  It's amperes x
> turns (I x T) that generates the primary flux which is what excites the
> secondary.  2.  One can best increase I x T by increasing I in preference to
> T.  This is because, while I varies directly with applied voltage V, the
> primary's impedance varies as the square of T and thus I will vary
inversely as
> the square of T.  And because of that, to maintain the same I while
increasing
> T, V must increase as the square of T, whereas in maintaining the same T
while
> increasing I, V must increase only directly with I.  3.  Thus, make V high
> while keeping T low.  Does that make sense?  Perhaps that's already a "given"
> in the coiler community.
>
> Ken Herrick