Re: OLTC Multi Primary

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Winston,

On 14 Aug 2002, at 6:23, Tesla list wrote:

> Original poster: "Marry Krutsch by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <u236-at-earthlink-dot-net>
> 
> Hi All,
> 
> 	I don't know whether or not the drawing/idea was mis-understood or not,
> but I'll explain the idea again.  I discussed this with Terry a few
> weeks ago, and he thought that it was too complicated.  I still don't
> think so, but then again, I'm not the one trying to build it and get it
> to work without smoke entering the picture ;-)).  I also don't have the
> fancy computer modeling stuff that Terry has (I can't even imagine how
> much that aids in designing circuits).
> 
> 	Anyway, the idea was not only for each transistor to have its own
> capacitor, but for each one to have its own complete tank circuit,
> identical to the others.  The main point to this was keeping the
> resonant frequency in the "normal" TC range by keeping the Fres of each
> tank high, while keeping the total energy in all of the caps (tanks)
> high enough to do some good at low (120 BPS) break rates.  That way, the
> secondary coil wouldn't need to have 0.5 Henries of inductance =:-0, and
> would therefor be less of a pain to build.

If the primaries are bundled, the coupling between each would be 
close to 1. It might as well be a single conductor. The total 
inductance of the bundle would still be that of a single conductor. 
In effect, it reduces to Terry's multiple capacitor/switch 
arrangement.  

> 	Also, using this method, power-per-break can be increased without
> further lowering the operating frequency, if the coil is running
> directly from the line and not DC.  The current consensus (I think) is
> that the prototype OLTC will run on DC.
> 
> 	The idea was to wind all the "separate" primary coils into a bundle,
> like Litz wire, so that no one tank would see too much more kickback
> than the others, and so the secondary coil would "see" only one
> primary.  Running at such a low frequency means that, using a
> "conventional" TC tank setup, you must lose either primary inductance,
> or capacitance.  Each one has its inherant problems.  The multiple tank
> circuit method allows you to in effect, lose neither one.  I know that
> an IGBT is a little different from a sparkgap ;-)), but their function
> in the circuit is the same.
> 
> 	Current sharing is less of a problem, since there are no transistors in
> parallel.  The firing timing issue is the same as with the current
> setup.  And, a problem with one circuit should not affect the others, so
> a catastophic "dominoe effect" failure would be less likely.  The wire
> used in each tank would be much smaller than that used in a single
> larger one, so making and manipulating the setup would be easier.  There
> were some other perks to this (I think), but I've forgotten them.

But the coupling constant between the bundled conductors *is* almost 
1. The separate primary circuits will not be separate at all and each 
will see the effects generated by its mates.

Regards,
Malcolm
  
> 	I did some math, and worked out a coil that runs at 70kHz, with a TOTAL
> primary capacitance of 30uF.  It has 10 tanks, each with a 3uF cap, and
> a 1.75 turn, 4.5" radius, 1.72 uH primary.  The total energy stored at a
> peak voltage of 320 is 1.56 joules.  The primary would in reality be 1
> turn.  The extra 0.75 is to account for off-axis inductance (tank
> wiring), and other stray effects.  If anything, this should be lower. 
> The secondary is 27.5" (wound), 2175 turns, and 6" in diameter.  The
> toroid is a modest 6" by 20".
> 
> 	Lastly, I should say that I'm sure that there are problems with this
> idea that I can't see, since I'm not know for my intelligence ;-)).  So,
> I invite the gurus of TC'ing to pick this clean.  I know I'll learn
> something from that.  I also don't mean to question Terry's judgement. 
> I wouldn't have mentioned this idea on the list, but since someone
> brought it up, I though I'd explain it.  Terry is right in keeping
> things simple for the first try.  This can be explored later (if at
> all).  I left some stuff out, but I'm getting tired (it's 12:45 am, and
> I've got work tomorrow).  
> 
> 	Sorry for such a long post.  I didn't intend for it to be that way
> ;-)).  Thanks for reading,
> Winston K.
> 
> 
> Tesla list wrote:
> > 
> > Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
> > 
> > Hi Jonathon,
> > 
> > At 10:49 AM 8/13/2002 -0400, you wrote:
> > >Hello everyone, esp. those on the OLTC scene...
> > >
> > >Looking through hot-streamer-dot-com/temp, whatever happened to the Multi
> primary
> > >idea?
> > >(hot-streamer-dot-com/temp/OLTC_Multi_Primary.jpg)
> > >Too much coupling? Too Complicated, or too many priamry coils ( > 10 )
> > 
> > It just seems too complex and ten primary loops may reduce the inductance
> > of the primary too much.  "I" also worry that the voltages on each loop may
> > not stay in sync with each other.  It just had a few unknowns and no real
> > reason to go that way.  I am trying to keep everything as basic and simple
> > as possible, pleanty of time later to make things complicated ;-))
> > 
> > Cheers,
> > 
> >         Terry
> > 
> > >
> > >I think having each IGBT with its own cap is a great idea, i would have
> never
> > >thought of that!
> > >
> > >Keep up the good work!  Hot-streamer-dot-com/OLTC now exists, but is under
> > >construction.
> > >
> > >---------------------------------------
> > >Jonathon Reinhart
> > >hot-streamer-dot-com/jonathon
> > >
> 
> 
> 
>