[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Solid state gaps beginners questions? (fwd)



---------- Forwarded message ----------
Date: Thu, 07 Jun 2007 16:30:44 -0400
From: Scott Bogard <teslas-intern@xxxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: Solid state gaps beginners questions?

Hey everybody,
     Since everybody is talking about this "SISG" I have a few simple easy 
to answer questions, as a "never touched solid state" person.  Obviously 
these SISGs are more efficient, lending to much bigger arcs, but what are 
the streamers like?  Do they look like conventional TC streamers, or are 
they like the swords produced with tube coils?  I've read that DRSSTC 
streamers look exactly like conventional streamers, what is the difference 
between DRSSTC and SISG?  People have been talking about "triggered SISG", 
what does that mean?  Final question, a short while ago, I suggested 
building a rotary "full contact" spark gap, I haven't started it yet, but my 
question is this, could one simply string a whole bunch of transistors ?(or 
mosfets, or whatever) in series, to obtain the necessary voltage rating, and 
than put strings in parallel for the necessary current rating of tank 
discharge, (like an MMC, but with transistors) and then trigger the bases of 
all of them simultaneously with a low voltage, full contact "spark gap" to 
fire the solid gap (actually, if my knowledge serves me well, the contact 
gap would have to cease fire, or shut off power to the transistors to fire 
the main gap).  Any thoughts on this?  Do I have the right idea, or do I 
have no clue what is going on!?!  Just curious.
Scott Bogard.


>From: "Tesla list" <tesla@xxxxxxxxxx>
>To: tesla@xxxxxxxxxx
>Subject: RE: Solid state gaps - what happened? (fwd)
>Date: Wed, 6 Jun 2007 22:05:10 -0600 (MDT)
>
>
>---------- Forwarded message ----------
>Date: Wed, 6 Jun 2007 22:08:25 -0500
>From: Mark R Dunn <teslamark@xxxxxxxxxxxxx>
>To: 'Tesla list' <tesla@xxxxxxxxxx>
>Subject: RE: Solid state gaps - what happened? (fwd)
>
>
>
>Gary:
>
>
>
>There have been plenty of posts on SISG, but little discussion.
>
>My SISG coil has been in operation since June 2006 and the current 
>technical
>info is available at:
>
>
>
>http://www.teslaboys.com/SISG/index.html
>
>
>
>I have shipped SISG boards to a number of coilers on the list.
>
>
>
>My coil uses (2) MOT's and (4) SISG boards(16 circuits X 900volt).
>
>Typically I tap at 13 or 14 circuits so I am running at 11.7 to 12.6 KV
>threshold voltage).  The SISG is elegant compared to a spark gap.  From my
>perspective the spark gap is history.
>
>
>
>My camera hasn't produced very good pics of the streamers, but a couple of
>weeks ago I did a demo for Steve Ward and Jeff Larson.  Jeff got some great
>pics and when I get them I will put them up on the website.
>
>
>
>My coil normally runs in the basement and I have it severely current 
>limited
>to keep the sparks off the walls, sewer pipes, equipment, etc.  Right now 
>it
>runs with 3 to 4 foot streamers, but I am only feeding the MOT's around
>82-85 VAC.  Cranked up to 100 to 110 VAC, it can do 5 to 6 footers, but I
>can't do extensive testing of that indoors and have not had time for
>extensive outdoor testing (My kids play Travel Soccer AND Baseball).
>
>
>
>The quenching has not been an issue.  The waveform decays on its own in
>about 40 uS.  As a result we have been able to decrease the gate shut-off
>resistor value to as low as 680 ohm.  There are waveforms on the website.
>
>
>
>One of the tricky issues with SISG is that you cannot independently control
>BPS.  (Note: Finn Hammer built a triggered version)  You control BPS by
>balancing the tank cap size against the impedance of the transformers.  
>This
>concept seems a bit hard to grasp for some people - I did not get it at
>first myself.  When I first fired up my SISG coil, my tank cap was way to
>small for my transformer impedance and my BPS was 1200!  Now that I have a
>properly sized tank cap, I run around 120 BPS.
>
>
>
>You mentioned cost...I think you will find that by the time you finish a
>good rotary spark gap, the cost is far greater than SISG.
>
>
>
>Terry pulled his Piranha site down because of a lack of the lack of respect
>that some coilers expressed regarding the safety issues regarding the tank
>circuit.  These MOT based designs can push 200 mA into the tank circuit
>during charging and because of the diodes SISG is a pulsed DC design.  
>There
>is real danger that the tank cap can remain charged on shutdown.  I have
>checked mine with HV probe and it takes about 60 to 90 seconds to discharge
>thru the safety resistors paralleled with the caps in the MMC.
>
>
>
>I have ongoing off list discussions with TCML members concerning SISG 
>weekly
>and sometimes daily.  The posts I and others have made to encourage
>discussion have for the most part been ignored so we figured that most
>people were not interested.
>
>
>
>Mark
>
>
>
>
>
>
>
> >---------- Forwarded message ----------
>
> >Date: Wed, 6 Jun 2007 15:29:06 -0400
>
> >From: "Lau, Gary" <Gary.Lau@xxxxxx>
>
> >To: Tesla list <tesla@xxxxxxxxxx
>
> >Subject: Solid state gaps - what happened?
>
>
>
> >Just about a year ago Terry Fritz came up with a very clever, modular
>
> >IGBT-based replacement to the static spark gap.  While the price tag was
>
> >steep and far more complex than conventional gaps, the reported
>
> >efficiency gains seemed hard to ignore.  It wasn't clear to me if the
>
> >SISG was truly a drop-in replacement to conventional gaps, but it seemed
>
> >to hold great promise, considering the ever-decreasing cost of silicon.
>
> >I recall there was ongoing work on triggered versions too.  I don't
>
> >recall if quenching (or lack there-of) was thought to be an issue.
>
>
>
> >Now a year later, not a word to be heard on the topic.  I'm just
>
> >wondering - was the cost just too high and the practical efficiency gain
>
> >didn't merit the cost, or if one is going the spendy/complex solid state
>
> >route, DRSSTC's do better, or did we just forget about it without Terry
>
> >to tout it?
>
>
>
> >Regards, Gary Lau
>
> >MA, USA
>
>
>
>
>
>
>

_________________________________________________________________
Need a break? Find your escape route with Live Search Maps. 
http://maps.live.com/default.aspx?ss=Restaurants~Hotels~Amusement%20Park&cp=33.832922~-117.915659&style=r&lvl=13&tilt=-90&dir=0&alt=-1000&scene=1118863&encType=1&FORM=MGAC01