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

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Wed, 6 Jun 2007 15:11:43 -0700 (PDT)
From: Brett Miller <brmtesla2@xxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Solid state gaps - what happened? (fwd)

Gary,

--- Tesla list <tesla@xxxxxxxxxx> wrote:

> 
> ---------- 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.  

Well, I built one (SISG) last week, using a different
IGBT which lacked an internal anti-parallel body
diode.  I had a stock of MUR860's left over from my
SSTC experiments and I added these in place of the
IGBT diodes.  With two segments and a single MOT I am
getting 2 inches of roaring power arc at 25v on the
variac...however, my tank cap is way under rated, as
it is a single CD 942 150nf cap.

I'm also in the process of designing my first DRSSTC,
but I loved the elegant simplicity of the SISG, and
after reading Terry's SISG.pdf a few times, I couldn't
resist the urge to build a prototype.  My IGBT's are
Fairchild G27N120BN and were just some I had sitting
in a box from an impulsive ebay purchase made when I
did not know that a "D" in the part number indicated
the body diode was present.  

> 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.

It "can" be a drop-in replacement to conventional
gaps, but it also goes places where conventional gaps
can scarecely tread...such as switching the relatively
low voltage of a single MOT.

Whether it fulfills Terry's dreams from the original
posts or not isn't really that relevant in my opinion.
 It is so cool and simple it doesn't really matter! 
It has revitalized my (once dead) interest in
disruptive coils.  Once you twiddle the controls of a
growling SSTC and can change the color, thickness, and
sounds of sparks...SGTC's tend to pale in comparison. 
The intrigue of solid state coils such as the DRSSTC,
SSTC, DF-DRSSTC, and OLTC is compelling.  It is really
not very complex either...it's just trendy to say
that, plus I think it helps a lot of people justify
the fact that they are sitting around saying that. 
Just look at the DRSSTC wiki at 4hv.

> 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.

It didn't stop Mark from getting 40+ inch sparks,
Terry 30+, or Finn Hammer from getting 60 with his
brick switched BRISG.

> Now a year later, not a word to be heard on the
> topic.  

In some places people are talking about it.

> 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?

The IGBT cost is high right now, but I'm so happy with
this I'm going to buy them anyway.  As far as "vs
DRSSTCs go"....some people definately did decide to go
the drsstc route instead, but I think "real coilers
should build both".  Ideally we'd like to have as many
people participating in as many of the topologies as
possible, just to maximize the chance of a
breakthrough/discovery.  There is not a thing complex
about the SISG.  It is easy to understand and
implement.  Keep away from the primary circuit while
the power is on.

4 years ago, I was scared of solid state, I suppose I
was afraid of failure, and the unknown.  Once I jumped
in...new year this year, I realized it wasn't any
harder or more complex than anything else.

I hope I have at least slightly raised the bar of
optimistic thinking on the TCML.  I have to admit the
stagnation has kind of bummed me out lately.

Oh...and soon I'll have pics and videos of my SISG
system for those who are interested.  

Cheers,

-Brett

> Regards, Gary Lau
> MA, USA




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