Re: New SSTC and topology in need of review

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

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

Hi,

Gary's SSTC was impressive, and higher voltages were needed for his design. 
In his design, the
secondary was directly driven without any primary coil, so to get a good 
impedance match, he
needed high voltages. If you use a primary coil, you should be able to just 
reduce the amount of
turns to get the impedance match. I believe his coil worked well because of 
the high peak power,
and not the high drive voltage. I don't know enough about Dan's system to 
comment on it.

The magnetizing current should go down, but it goes through more MOSFETs in 
series, so it should
cancel out there. The magnetizing VA should be the the same compared to the 
real VA also.
Magnetizing current is not only bad for conduction loss, but it also 
introduces switching loss
that would be otherwise very small :-(. An easier way to do it would be to 
use a resonant
capacitor in series. You can get impedance matches easier, no magnetizing 
current, and your high
voltage (across the primary). High coupling would no longer be needed either.

I don't understand why the current would skyrocket. How much does it 
increase? At half the turns,
I would expect about 4 the current, depending on the streamer load. Is it 
significantly different?
Do the sparks seem brighter? The only thing I can think of is that the 
effective coupling goes
down due to stray inductance leading to the primary, but that shouldn't be 
significant until down
around 1 or 2 turns. Can you think of an explanation?

Wait a minute... I now remember someone (Dan Mccauley?) found the resonator 
to look like a current
sink. That means that if you cut the turns in half, you get 4x the 
magnetizing current, but twice
the in phase current. That could be it. In that case, I think you would 
just need a lower
impedance resonator. If what I said is right, then it isn't that you need 
at leat 5 turns, it's
that the resonator doesn's want more power. The same thing should happen at 
20 turns if you do a
four stage circuit like yours. Make sense to anyone?

There may be more to it, but I think the flyback works better because there 
is less current
flowing through the same MOSFETs, and it is more efficient. The more 
MOSFETs in series should
remove this benefit :-(

It sounds like a cool project, and we'll see if higher voltages do help. 
Good luck!

--- Tesla list <tesla-at-pupman-dot-com> wrote:
 > Original poster: "Steven Ward" <srward16-at-hotmail-dot-com>
 >
 > Well Jimmy, im not entirely sure what i am going to gain, but i at least
 > *think* it should be worthwhile.  Dan McCauley mentioned that his MOT SSTC
 > (when working quite a while ago now) produced extremely long sparks.  Also,
 > Dr. Gary Johnson has a large SSTC running 1700VDC into a half-bridge.. his
 > coil makes some 54" sparks if i remember, though it IS powered from a PT.
 >
 > Basically, my thought is that magnetizing current could be reduced a bit,
 > and i can more easily get an impedance match that would give lots of power
 > throughput without half of the current going to Imag.  With my 170V SSTCs
 > ive gotten down to 5 turn primaries that are some 8" tall.  Very tight
 > coupling and very few turns.  But, each turn taken off makes the current
 > input skyrocket but does very little to increase spark length.  It just
 > SEEMS that you need higher voltages.  As to how high, i dont know, but
 > 1400V seemed like a *fun* place to begin.
 >
 > I must also note how my half-bridge flyback driver reacts with low
 > voltage/high current (few primary turns) power supplies and high
 > voltage/low current (many primary turns).  At low voltages the flyback has
 > several resonant frequencies and makes decent sparks (with some
 > heating).  But, at 120V input, i get disasterously long sparks but only 1
 > Fres, and with no heating of components at all.  I know we are talking
 > about 2 completely different things here, but i dont see why this concept
 > would not hold up with SSTCs.
 >
 > Steve Ward
 >
 >
 >
 >
 > >From: "Tesla list" <tesla-at-pupman-dot-com>
 > >To: tesla-at-pupman-dot-com
 > >Subject: Re: New SSTC and topology in need of review
 > >Date: Sun, 14 Dec 2003 10:53:49 -0700
 > >
 > >Original poster: jimmy hynes <chunkyboy86-at-yahoo-dot-com>
 > >
 > >Hi,
 > >
 > >I remember seeing that circuit too, and thought it was pretty cool. What
 > >do you expect to gain
 > >from a higher input voltage? The only thing I can see is the increased
 > >number of primary turns
 > >needed for an impedance match. Unless you are using 1 turn on normal
 > >SSTCs, I don't see the
 > >benefit.
 > >
 > >--- Tesla list <tesla-at-pupman-dot-com> wrote:
 > > > Original poster: "Steven Ward" <srward16-at-hotmail-dot-com>
 > > >
 > > > Hi everyone,
 > > >
 > > > I have been working out my latest SSTC designed in the hopes that higher
 > > > voltage across the primary coil will work better than typical low 
voltages
 > > > of some 170-340V.  This new design should be able to produce about 1400V
 > > > across the primary in a very unique way:
 > > >
 > > > http://www.hot-streamer-dot-com/srward16/SSSSTC.htm
 > > >
 > > > Ive been studying this topology for a long time now and im in the 
process
 > > > of building this thing because i just have to see it for myself.
 > >Basically
 > > > i would like for you guys to analyze this topology and give me some
 > > > feedback on potential problems/benefits i may see.  I look forward 
to what
 > > > the solid state experts say.  Maybe this will lead to a new avenue 
in solid
 > > > state tesla coiling... though i have a feeling many would not like to
 > > > reproduce a 16 fet design (or 32 fets if things go well :O).
 > > >
 > > > So lets hear it! what do you all think?
 > > >
 > > > Thanks,
 > > >
 > > > Steve Ward
 > > >
 > > >
 > >
 > >
 > >=====
 > >Jimmy
 > >
 >
 >


=====
Jimmy