Re: Off Line - DRSSTC (OL-DRSSTC) - 3

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>

Hi DC,

At 01:02 PM 9/28/2005, you wrote:


> If you make it 4 ---- 50 uF Electrolytics, then each unit should be 
> seeing around 5 amps each which should allow them to live assuming 
> they are quality units.  Will your design allow you to go to 200 uF 
> total capacitance?  This would make each cap 50 Uf and help spread 
> the power around a bit.  Copper strap would provide the 
> interconnections to keep the peak current values high.

I have dropped the voltage and played with power so 40  22uF 200V 
caps will now work.  The caps completely charge and discharge 60 
times a second so the ripple current is rather enormous!


> Perhaps a few small 2-3 Ohm, 20 watt equalizing resistors could also 
> be added across each each cap to keep the  current flows equal, 
> however, this might reduce the overall peak current --- perhaps undesireable.

They have to take the full primary current so no added 
resistance.  Since they are in an AC circuit, they should load share 
automatically.


> Have you some up with any general design for the primary, sec, and 
> topload requirements?  I was thinking of an 8 inch dia. PVC 
> coilform, 14 x 5 load, 2,500 turns on the sec coil, aspect ratio of 5.5:1.

Any coil should work that is say 150kHz or less.  The primary cap and 
all needs to be made so the peak primary current is within the range 
of the IGBTs.


> This is an exciting concept and I look forward to building one asap.

Ok, but it has never been done so no guarantees ;-)  The circuit 
design changes all the time.

Cheers,

        Terry



> Dr. Resonance
>
>
> > Hi All,
> >
> > I have been running a lot of models and now have this for the OL 
> > -DRSSTC concept schematic:
> >
> > http://hot-streamer.com/temp/OL-DRSSTC-03.gif
> >
> > I had to go to 60BPS instead of 120 BPS.  I use the dead 1/2 cycle 
> > to fire the coil so there is no incoming current to quickly 
> > recharge the buss cap. Otherwise, once the coil is started, in 
> > never turns off!!  The waveforms look like this:
> >
> > http://hot-streamer.com/temp/OL-DRSSTC-03a.gif
> >
> > It should put out nice 60BPS bursts with 200kV peaks.  Very long 
> > 2mS duration.  Power to the streamer is roughly 1080 watts.  The 
> > resonant charger gets the cap up to about 520VDC firing voltage 
> > with the line and resistive losses (note that the inductor is 19mH 
> > now for 60Hz).  It is a stunning 25 joules per bang!!!
> >
> > The primary current is only 200 amps and everything else seems 
> > generally easy without massive over loads.  The 50 ohm resistors 
> > across the gates reduce the gate voltage and act a bit like a dead 
> > zone for the IGBT crossover.
> >
> > The trigger circuit is pretty much out of the SIDAC data sheet...
> >
> > The only concern is the 185uF buss cap.  It will see about 22A 
> > RMS!  That would kill most single electrolytics so I will have to 
> > look into that more.
> >
> > By changing the SIDAC value, it should work off 120VAC or a variac 
> > at lower test  voltages too.  Everything can be "fiddled with" as 
> > needed to make adjustments or to get it to work.
> >
> > So it is looking pretty good on paper and by computer.  I think I 
> > will order some parts...
> >
> > Cheers,
> >
> > Terry