Re: ALF: why not DRSSTC?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx>

Tesla list wrote:

> Original poster: Greg Leyh <lod@xxxxxxxxxxx>
> ...
> Jimmy Hynes wrote:
>
> > What's your trick for doing it "quickly"? The DRSSTC also sucks the 
> > energy back out of the secondary. If you don't think it's quick 
> > enough, we could probably implement the same sort of 'trick' you 
> > got to do it quickly.
>
> No tricks, other than higher coupling and accurate quenching.  Also, 
> if one chooses a coupling value near one of the 'Magic-k' values, 
> it's possible to achieve both zero-voltage and zero-current switching.
> However, if you transfer the energy that fast, is it still a 
> DRSSTC?  At what point does it become a standard impulse-type TC?
>...

A DRSSTC can be made to generate almost the same waveforms of a
capacitor-discharge system, but the systems are different.
The fundamental difference is that a capacitor-discharge system
operates using the zero-input response of the network, and the
DRSSTC uses the zero-state response, with a sinusoidal (or square
wave with negligible difference) input.
Operation with feedback falls into linear operation if the system
is properly tuned, and the load doesn't vary much.
The general case with feedback is difficult to analyze, and can
even (probably) result in chaotic behavior.
A capacitor-discharge system that produces the same output of a
DRSSTC would be a kind or a magnifier (with a different structure,
but a 6th-order system), where the primary capacitor and the
primary inductor are very large, so they oscillate for long time
losing very little energy for the remaining system. Replace this
tank by a sinusoidal voltage source, and you have the DRSSTC structure.
The output waveform contains three oscillations, and not just two.
The operation in bursts of a DRSSTC is needed because
the components used would not tolerate continuous operation. And
also because with feedback there is strong tendency of the system
to lock into one of the resonances of the system, and then the
input current grows limited only by resistive losses, or limits
in the power supply. The same, of course, happen if feedback is
not used but the drive is at one of these (two) frequencies.

I have a DRSSTC designer/simulator here (sstcd):
http://www.coe.ufrj.br/~acmq/programs
(Still can't design systems operating exactly at the resonances,
but can simulate them.)

Antonio Carlos M. de Queiroz