Re: Solid state gaps beginners questions? (fwd)

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---------- Forwarded message ----------
Date: Fri, 08 Jun 2007 16:12:56 +0200
From: Finn Hammer <f-h@xxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Solid state gaps beginners questions? (fwd)



Tesla list skrev:
> ---------- 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?
Perhaps "much bigger arcs" is pushing it, but surely the SISG is very 
efficient.
The advantages lie in other areas, I think.
But first to your questions. A SISG coil is disruptive, and acts like an 
ordinary disruptive coil equipped with a static gap. This gap has a very 
accurate turn on voltage, which does not change while running, like many 
static spark gaps tend to do, due to heat dissipation problems.

   People have been talking about "triggered SISG",
> what does that mean?  

The ordinary SISG uses a string of SIDAC`s to clamp the voltage across 
the IGBT`s while they turn on. This means that the IGBT is made to 
conduct at a fixed voltage threshold and this is only good for certain 
purposes. Like if that is what you go for. A consequence of this is a 
fixed or perhaps erratic breakrate. But an uncontrolled breakrate.
If you wold like to controll the breakrate, ome sort of trigger 
circuitry has to be incorporated. This is done by placing a thyristor in 
parallel with the majority of the SIDAC`s, and then force it into 
conduction by a trigger pulse into a gate transformer.
This sort of retires the SIDAC`s into acting as "safety gaps" to insure 
that the IGBT`s are kept below thair peak voltage rating.


Cheers, Finn Hammer