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Re: ALF: why not DRSSTC?

Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>

Hi,

I guess I should say something :o)

The OLTC is a rock solid "not much that can go wrong thing"... Greg certainly has the IGBT knowledge!!!

But the DRSSTC is the much better performer with vast capabilities...

"I" would "start" with the OLTC design. But leave the "option" of going to DRSSTC "wide open" baby!!!

The ALF is a "BIG" project by any standard. Best to stay with rock solid stuff to get it up and running and make the investors happy ;-)) Then, going to DRSSTC should not be a great leap...

The DRSSTC is definitely "leading edge"! But with the giant investment in the ALF project, the "bleeding edge" also has to be avoided!!!

So I would play the conservative approach, and be ready to jump to the "wild side" as the money pours in :-))

Like the clever chameleon, keep the options open for change as and if needed... But at this level of investment "screw ups" are not an option...

Almost stunning to note that the spark gap is not an option either :-)) Tesla would have been... confused =:O Till he saw the light :-)

Cheers,

        Terrry



At 10:48 PM 9/20/2005, you wrote: 
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 <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
>
>
>
>