RE: DRSSTC thoughts...

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>

Hi Steve,

At 04:28 AM 10/4/2004, you wrote:
> >Maybe Steve
> >C. can comment
> >on the models he's been using.
>
>Wow. It seems DRSSTC fever has finally hit Pupman :P

It was a little too high tech for most of use to "get"...  Steve's 130+ 
inch streamers, and now Dan's great book to explain it, allows the masses 
to finally catch on ;-))


>First of all, here is the PSpice simulation I use.
>http://scopeboy-dot-com/tesla/drsstc/drsstc.zip

Should have been per your correction:

http://scopeboy-dot-com/tesla/drsstc/drsstc_sim.zip

Gosh!!  You read the MicroSim instructions didn't you ;-)))  It works fine, 
but I will have to spend more time figuring out what is going on...  BTW - 
You can "select" the silly title block and just delete it...  It is just 
blocks and default added text.


>Maybe Terry and Dan Mc would like to play with it. There are two
>simulations, each has a preset list of displays and commands for Probe. If
>you run the .cmd file in Probe, several plots should appear showing useful
>stuff.
>
>It uses the parametric simulation feature to simulate the coil dozens of
>times with different streamer loadings, and see the worst-case currents and
>voltages. The expected spark length can also be predicted. There is another
>simulation file that does the same but with different primary inductances,
>to help you find the correct tuning point.

I was never able to get that parametric thing to work.  It could have saved 
me weeks!!!  Now that there is a model with it working, I shall try and 
figure it out!!


>Qualitatively this sim seems to work quite well. It predicts the doubling of
>primary current for extreme impedance mismatches (like heavy ground arcs)
>and so on.

Dan's new book shows exactly that!!!

>And it also does a reasonable reproduction of the bizarre
>waveform from my Tesla-2 run as a DRSSTC. But quantitatively it still has a
>way to go!

Just a matter of tweaking the values in.


>To try and refine the model I am starting a series of streamer loading
>experiments (these are a joint venture with the high voltage technologies
>group at Strathclyde university)
>
>http://scopeboy-dot-com/tesla/experiment/

Cool!  It takes some real fancy equipment to refine the values and numbers 
and all.  Expensive stuff!!  Best if it can be borrowed ;-))


>I'm using a similar method to what Terry did but over a wide range of
>breakrates and bang energies (which can be accurately controlled on the OLTC
>II) I have hardly any data yet, the little I do have suggests that a 36"
>streamer at 100bps, 66kHz has a shunt resistance of about 400k.

I think you asked about streamer impedances...  It's been a long time, but 
check here:

http://www.pupman-dot-com/listarchives/1998/October/msg00290.html

http://hot-streamer-dot-com/TeslaCoils/MyCoils/CWCoil/CWImpedance.txt

I wish others could add to this data...  I hate to be the only one "making 
these numbers up".  I have been known to screw up :o)))

>So far, I think that we can adequately model the streamer load as either a
>series RC or a shunt RC circuit. This is a "rough approximation" that only
>holds at a single frequency. But since the DRSSTC's output only contains a
>narrow band of frequencies I don't see a problem.

They are an excellent tool for measurements!!  They don't have spark gaps 
and such burning up and all the complexities of goofy spark gap coils going 
on.  The OLTC is very "tame" too but the DRSSTC simulates coils that are 
far more common.


>I assume that the R and C vary in some way as a function of streamer length.
>At the moment I believe that R is proportional to (1/Length) and C is
>proportional to Length. But I wouldn't be surprised if there turned out to
>be a squared or square root in there. The constant of proportionality will
>probably depend on many things too, for instance the breakrate and the
>resonant frequency.

Cool!!  Earlier data (known as "old data") suggest R is very constant and C 
is directly proportional to streamer length.  But "new data" is very 
welcome ;-)))

Cheers,

         Terry



>Steve C.