Re: SISG and primary voltage.

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "J. Aaron Holmes" <jaholmes@xxxxxxxxxxxxxxxxxx>

Thanks, Steve (and Terry, who also replied earlier),
this helps!  I'll probably take my first swing at this
with a MOT pair or other 3-4kV source, as this has
proven to work (for Terry, at least ;-))  Maybe then
I'll pick up a big brick and try something lower-V and
higher-C :-)  I'd love to see what somebody could
accomplish using only a single SISG section as
currently specified, though.

Best Regards,
Aaron

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

> Original poster: "S&JY" <youngsters@xxxxxxxxxxxxxxx>
>
> Aaron,
>
> One important reason for using higher voltages
> relates to the energy that
> gets stored and released in the primary "tank"
> capacitor (e.g. MMC).  The
> energy is 0.5 * C * V * V  (half CV squared).  In
> other words, the stored
> energy goes up as the square of the voltage.  So
> comparing a 100 volt supply
> with a 10,000 volt supply, the "bang" Joules would
> increase by a factor of
> 10,000.
>
> Thus, to use lower voltages and maintain the same
> bang energy, the tank
> capacitor size would need to be increased
> significantly, requiring the
> primary inductance (turns) to be decreased
> substantially to stay in tune
> with the secondary.  This usually is not good
> because higher inductance
> primaries are typically more efficient and reduce
> the stress on the primary
> capacitor.  Better is to substantially increase the
> secondary inductance (to
> lower the resonant frequency) to allow more primary
> turns with a bigger
> primary capacitor.
>
> The other thing one can do is increase the break
> rate which increases the
> average energy into the coil, which, up to a point,
> increases streamer
> length.
>
> That being said, some of the DRSSTC coils perform
> amazingly well using line
> voltage multipliers (several hundred volts DC)
> instead of transformers to
> power their coils.
>
> --Steve Y.
>
> ----- Original Message -----
> From: "Tesla list" <tesla@xxxxxxxxxx>
> To: <tesla@xxxxxxxxxx>
> Sent: Wednesday, May 24, 2006 10:34 AM
> Subject: SISG and primary voltage.
>
>
>  > Original poster: "J. Aaron Holmes"
> <jaholmes@xxxxxxxxxxxxxxxxxx>
>  >
>  > I've been following the SISG threads
> closely...even
>  > ordered parts to play with!  But my experience is
>  > primarily with classical SGTCs, and my grasp of
> the
>  > theory largely limited to rules of thumb, so I'm
> a
>  > fish mostly-out-of-water with all this
> solid-state
>  > stuff! :-((
>  >
>  > In particular, it occurs to me that I now no
> longer
>  > understand why one would opt for a HV transformer
> with
>  > SISGs around.  I've got more ~2kV MOTs than I
> know
>  > what to do with, but why even go *that* high?
> Why not
>  > take an OLTC-ish approach and charge the caps
> straight
>  > from the rectified mains?  With SGTCs, the
> importance
>  > of quenching and the difficulty of quenching at
> low
>  > voltages seems to dictate that some amount of
> HV-ness
>  > is *required*, not just *good*.  With the
> quenching
>  > argument gone, can somebody attempt to explain
> (for
>  > the non-EEs among us--me included!) why one might
> opt
>  > for a HV SISG coil versus a LV one?  I'm sure
> there
>  > *are* reasons for one over the other (i*i*r
> losses,
>  > perhaps?), but the factors aren't all obvious to
> me.
>  > Some people are all about efficiency, but if
> similar
>  > output can be achieved in the SISG coil by losing
> the
>  > HV transformer and bearing some IGBT heating
> instead,
>  > that would also be "cool" :-)
>  >
>  > ---
>  >
>  > Thanks, Terry and company, for proving that
> modern
>  > technology might actually be able to *simplify*
> coil
>  > construction :-))  Always thought it had to be
> so, but
>  > I've seen relatively few examples of it until
> now.
>  >
>  > Regards,
>  > aaron
>  >
>  >
>  >
>  >
>  >
>
>
>