Re: ALF: why not DRSSTC?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>

HI Steve,
          If I had to hazard a guess it might be something to do with
duty cycle and overall heating. ?  OLTC topology would come into its
own at ALF frequencies but I agree that the differences in cap sizes
and primary inductances is becoming a moot point down there.

?
Malcolm

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
>
>
>
>