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Re: Re: [TCML] SSTC full bridge control system question



Michael Twieg 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.
For complete beats a set of particular relations among the inductances, capacitances, and coupling coefficient must exist. Nothing very critical, as the element values used in a normal SGTC are usually pretty close to the tuning required for an SSTC working in "notched" mode, in one of the many possible modes (but not identical). I define the "mode" by three numbers that define the ratio of the two resonance frequencies of the system and the excitation frequency (the excitation between the resonances). In the best design, the numbers are odd and have "double odd" difference, as 1:3:5 (difference=2, two times 1, that is odd). Usual systems will be around mode 37:39:41, as in the example in my page. Irregular modes are also possible, with differences between the odd numbers being 6 (2x3) or 10 (2x5), but there is no advantage in using them. Of course, streamer loading affects what is actually obtained, but the influence is similar to what occurs in a SGTC, that works with similar waveforms (actually, a magnifier works with
more similar waveforms).
It is really interesting that zero-current switching is natural in SSTCs operating in this way.

Antonio Carlos M. de Queiroz


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