Re: High Power SSTCs - Need help and opinions

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: jimmy hynes <chunkyboy86-at-yahoo-dot-com> 

Hi Dan,

--- Tesla list <tesla-at-pupman-dot-com> wrote:
 > Original poster: "Mccauley, Daniel H"
 > <daniel.h.mccauley-at-lmco-dot-com>
 >
 >
 > After doing a considerable amount of work with flea
 > powered SSTCs such
 > as the PlasmaSonic SSTC and my high frequency
 > tweeter system (which is still ongoing), I'm ready
 > to sit down and build
 > a monster SSTC capable of operating at many
 > kilowatts and hopefully put out huge, thick, and
 > nasty output streamers.
 > I have a large budget allocated for this
 > winter project so if it takes $2000 worth of high
 > performance FETs, so
 > be it.  But I want it to be nasty beast of a
 > SSTC.
 >

Cool ;-). You should look into IGBTs. Some can switch
pretty fast, and come with high voltage ratings. For
example, IRG4PH50K is a 1200v 45 amp IGBT with pretty
good switching times. There are faster ones too, but
with a big coil, it shouldn't be a problem.

 > There are currently two routes which are both
 > difficult in their own
 > regard.
 >
 > 1) Maximize output power utilizing maximum primary
 > voltage waveforms
 >     (Primary difficulty is switching high voltage
 > switch with solid state
 > devices)
 >

There are some good high voltage IGBTs, but powering
them would require heavy transformers. Better to avoid
that if you can.
 > 2) Maximize output power utilizing maximum primary
 > current waveforms
 >     (Difficulty in maximizing primary impedance and
 > current handling
 > capabilities of solid state devices)
 >

 >
 > I would like to use option number 2 and maximize the
 > primary current.  I
 > already believe Justin and Aaron have done
 > considerable work in this area.  My questions are:
 >
 > A.  There has to be some limit to the amount of
 > turns one can place on
 > the primary when trying to lower the impedance
 > of the primary to maximize primary current.  Once
 > this limit is reached,
 > what other alternatives are there for lowering
 > this impedance even more.
 >

Well, it seems to me that 1 turn would be close to the
limit, but you could do better by making a primary
with multiple turns in parallel. This would also
increase coupling which is good. You could also try
adding a series capacitor if the coupling is low, and
the coil is lightly loaded. Pspice is your friend ;-)

 > B.  Will building a rather large primary / secondary
 > coil system result
 > in even lower primary impedances???  Obviously,
 > thicker wire will have a
 > lower impedance, but what about coupling between
 > coils?
 >

It depends on how you normalize it. Are you talking
about same number of turns, same wire size? If
impedance matching is going to be tough, then I guess
you could play around with FANTC or something until
you find a low impedance. I think you should be fine
with one or two turns in parallel.

  Higher coupling helps by inducing more voltage on the
secondary, and there is leakage inductance. Or, for
the same power you can use more turns and have less
magnetizing current. It just depends on how you want
to think about it.

 > Throw out any and all opinions, comments, you can.
 > I do want to build a
 > SSTC capable of 10kW+.  Its going to be a challenge
 > (plethora of snubber
 > circuits, transmission line designed gate drivers,
 > FDFI, etc...), but it
 > will be fun!
 >
 > Dan
 >
 >
Good luck! I will be looking forward to it!

=====
Jimmy

_