Re: Parallel resonant DRSSTC

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Sue Gaeta <sgsparky@xxxxxxxxxxx>

Thanks to all who replied. Most seem to agree on the impedance matching 
being a very big issue. I didn't think of that, and it makes sense since 
the solid state circuitry utilises much higher currents.

>Original poster: "Steve Conner" 
<<http://us.f814.mail.yahoo.com/ym/Compose?To=steve.conner@xxxxxxxxxxx&YY=84617&order=down&sort=date&pos=0&view=a&head=b>steve.conner@xxxxxxxxxxx>
>"Just my $.20 worth on this-

>1) Parallel resonant DRSSTCs do exist. I have seen two made by Vladimiro
>Mazzilli and Liviu Vasiliu. The secret is to make the inverter 
current-fed rather than voltage >fed.They used the so-called "Royer 
oscillator"push-pull circuit with two IGBTs. IMO this >SSTC design is very 
simple and elegant and deserves more attention than it gets. But it's 
not >so easy to use in pulsed operation because of the choke in the DC link."
There are quite a few of you guys on 4HV using this circuit to power 
flyback transformers, and getting really phenominal flaming discharges. 
Very impressive. Burt Hickman also mentioned this circuit to me quite a 
while ago, and said that it is a very good circuit. I want to persue this 
as a SSTC project for the future. As of this morning, I am finished playing 
with the P460s and I am going to start working on my DRSSTC using the 45 
amp IGBTs. After I am done with that I want to play with a Royer circuit. 
As you said it looks like it needs more attention.

>"This is true. But remember that in the DRSSTC we need a very fast and 
violent delivery of >power to a resonator with a Q of about 10."

I like the way you worded that. "Violent delivery" :-)

>Original poster: "Black Moon" 
<<http://us.f814.mail.yahoo.com/ym/Compose?To=black_moons@xxxxxxxxxxx&YY=61015&order=down&sort=date&pos=0&view=a&head=b>black_moons@xxxxxxxxxxx>
>Just a random note, but maybe look at class C or class E rf amps? they 
effectively use solid >state parallel resonant circuits with low conduction 
time (or a ring circuit to provide low turnon >voltage/current in class E 
and hence very low turnon loss and extream efficancy 90%+)
I remember that I posted a link on here a while ago, where the guy went 
into a lot of detail about how to design class E transmitters. 
<http://www.classeradio.org/>http://www.classeradio.org/ I have to admit 
that I only read a little bit of it. I think I need to go back and study it 
more thoroughly now. Alot of it doesn't pertain to what we are doing but I 
think a lot of good info can be gleaned from that. Somewhere he mentions 
something about tuning out the output capacitance of a MOSFET so that it 
can be used at higher frequencies. I thought that it would be interesting 
to choose devices with an output capacitance that would be easily resonated 
with a primary, and a secondary would have to be designed for that 
frequency. I don't know how practical this would be since I have not really 
studied it in depth yet. The people who simulate circuits could probably 
figure out how rediculous this idea is relatively quickly :-)

>Original poster: "Bob (R.A.) Jones"
>An other way of looking at it is to note that a parallel L C is low 
impedance at all frequencies >other than resonance. So if you apply a 
square wave from a low impedance to it the harmonic >currents are huge 
because it effectively a sort circuit.

This square waves with all the it's harmonics is something I didn't even 
think about. That is a very good point!

>To address your particular question about almost no current thru the 
switched. That's not >true.  The current thru the switches is determined by 
the power you decide to pump in to the >system by selecting the primary 
turns, operating frequency and mode etc.

I was actually thinking of the massive ringing current that would flow 
between the primary and resonating capacitor if the parallel resonant 
circuit was used instead of series. When the switch closes current would 
flow through it to charge up the capacitor. I see your point, it would look 
like a short in the very beginning of the pulse.

Sue