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,

--- Tesla list <tesla-at-pupman-dot-com> wrote:
 > Original poster: "Malcolm Watts" <m.j.watts-at-massey.ac.nz>
 >
 > Hi Jimmy,
 >            I confess to having some difficulty following some of the
 > concepts expressed in your piece:
 >
 > On 14 Dec 2003, at 19:45, Tesla list wrote:
 >
 >  > 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.
 >
 > To get power into the base of a resonator does require a high voltage
 > feed as it is typically on the order of 50 Ohms unloaded. Using a
 > primary gets around this limitation and the higher the step-up ratio,
 > the more power you can get in.

Yep, until you run out of turns...
 >
 >  > 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.
 >
 > Are we talking about air-cored coils? The concept of magnetizing
 > current doesn't really apply in that case.
 >

Yes, air-cored coils. You can call it what you want, but I am talking about 
the out of phase
current that would flow with no secondary present.

 >  > 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?
 >
 > You can see the dramatic effects of reducing primary turns at quite
 > low powers (a few W) with a resonator, primary and lo-Z o/p signal
 > generator and scope (and fluoro tube if one is handy). Reducing the
 > primary turns causes the output to climb dramatically and it is not
 > related to the reactance of the primary as shown by tuning the
 > generator around the resonant frequency. Doing this also sucks a lot
 > of current out of the generator.
 >

How much of the extra current is reactive, and how much is in phase?
 > Malcolm
 >
 >  > 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
 >  >
 >  >
 >  >
 >
 >


=====
Jimmy