Re: Solid state gaps - what happened? (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Wed, 6 Jun 2007 23:52:42 -0500
From: resonance <resonance@xxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Solid state gaps - what happened? (fwd)



Mark:

Running your dual MOTs, what are you pulling for current on each MOT 
primary?   And, what cap value did you end up using to get the bps at 120?

Dr. Resonance
----- Original Message ----- 
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Wednesday, June 06, 2007 11:05 PM
Subject: RE: Solid state gaps - what happened? (fwd)


>
> ---------- 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
>
>
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>