Re: ALF: why not DRSSTC?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Dan" <DUllfig@xxxxxxxxxxxxx>

Hello all,

I'd like to post a related question, since you guys are talking about 
OLTC and DRSSTC's. I have this pretty big Thyratron collecting dust 
on a shelve, and was wondering if the OLTC circuit would lend itself 
to be run by the thyratron, instead of the IGBT. Seems to me that 
while the current is flowing backwards through the diode, current 
would fall to zero through the thyratron, and it cold turn off 
safely. Backwards currents through the thyratron are a no-no, as I 
understand, but this circuit seems to solve that problem.

I would probably put a diod in series with the thyratron to guarantee 
no backwards current.

Dan

PS.: in case you're wondering, the tube is a CX1622, about 12" long, 
35 kV, 5 kA...  :)
----- Original Message -----
From: <mailto:tesla@xxxxxxxxxx>Tesla list
To: <mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx
Sent: Tuesday, September 20, 2005 10:12 PM
Subject: Re: ALF: why not DRSSTC?

Original poster: Finn Hammer <<mailto:f-h@xxxx>f-h@xxxx>

All,

Having built 2 examples of OLTC and 6  identical DRSSTC`s I tend to
agree with Steves here. Of course. But should we not bear in mind
that the ALF project was conceived around 1997 at a time when nobody
had yet thought about the DRSSTC topology?.

Cheers, Finn Hammer



>On 20 Sep 2005, at 10:31, Tesla list wrote:
>
> > Original poster: Steve Ward 
<<mailto:steve.ward@xxxxxxxxx>steve.ward@xxxxxxxxx>
> >
> > Hello all,
> >
> > This message is particularly aimed at Greg Leyh, but I would like
> > comments from others as well.
> >
> > As far as i know (and i might be wrong) Greg is currently working on a
> > scale model of his ALF towers.  This prototype uses the OLTC topology
> > to drive the Tesla resonator.  Since silicon appears to be the weapon
> > of choice already, I'm curious as to why not DRSSTC instead of OLTC?
> > It seems (at least on our hobbyist level) that the DRSSTC can
> > outperform an OLTC for similar amount of silicon used.  The DRSSTC
> > also does not have the difficulties that the OLTC intruduces as far as
> > primary coils are concerned (many OLTCs are just 1 or 2 turn
> > primaries).  The DRSSTC also does not have to store the entire bang
> > energy in the tank cap (another benefit)
> >
> > One possible issue i could see is this:  1200V devices will only get
> > you so far until you are looking at using single turn primaries and
> > giant tank capacitors (resembling the OLTC, but this is even more
> > problem for OLTCs as they scale up as well).  So you might be forced
> > to look at 1700V or 3300V devices.  But I'm aware that these devices
> > also have their limitations (they are slower and have greater losses,
> > but i think these are not much to overcome).  Ive heard that the real
> > problem is from cosmic rays causing the devices to turn on or
> > avalanche (what is the exact mechanism?) when you don't want them to.
> > But, wouldn't this also be a problem with using higher voltage silicon
> > in the OLTC?
> >
> > So for each problem I see with scaling a DRSSTC to ALF size, it seems
> > an OLTC would have the same problems.  As I (and others) see it, the
> > DRSSTC is overall a better topology.  So to summarize: why OLTC over
> > DRSSTC?  I'm guessing Greg has thought about this more than i have, so
> > i would really like to hear his response.
> >
> > Thanks,
> >
> > Steve Ward
> >
> >
> >
> >
>
>