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The Ideas to Date
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From: Malcolm Watts [SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: Wednesday, June 03, 1998 4:31 PM
To: Tesla List
Subject: Re: The Ideas to Date
A few brief comments:
> From: terryf-at-verinet-dot-com [SMTP:terryf-at-verinet-dot-com]
> Sent: Monday, June 01, 1998 10:19 PM
> To: tesla-at-pupman-dot-com
> Subject: The Ideas to Date
>
> The following is a thread between myself and David Sharp of TCBOR. The
> material is rather heavy reading but we felt it should be shared with everyone.
>
> Terry Fritz
>
<snip>
> > >2. Vo is a function of resonator base current.
> >
> > Like Vo = Ibase * 2*pi*Lsec This equation is probably very near to
> > reality. Even though the resonating capacitance is split between Ctop and
> > Cself, the voltage on each is the same.
At the top you are saying? I think that relationship holds only if
current is the same throughout the length of the winding.
> > >2. Zp should be relatively high (not 20 ohms, more like 40-50 ohms)
> >
> > The optimal value will depend on all the calculations when the data is all
> > in. Perhaps the best value is higher than most people design for now? This
> > would seem to be suggested.
Agree. In fact the higher the better but this obviously impacts on
output voltage as the COE formula shows. Gap losses are reduced as Zp
gets higher.
> > >3. Lp should be > 75uH at tune point (100-150 optimum)
Depends on operating frequency. Low Lp does well in a small high
frequency system (Xp = 2.PI.F.L). The lower system frequency, the
higher Lp needs to go to keep Xp high.
> > >7. Fo of system should be less than 50kHz.
> >
> > Many advantages to running at low frequency. Sparks get a bit more
> > dangerous! But at this level, we aren't exactly trying to make our hair
> > stand on end with our coils :-)) One very interesting implication of the
> > standing wave theory going away is that Q may not be very important!! Let
> > me say that again... Q is not very important! We always wanted high Q to
> > help the standing waves ring up to a high value. If there are no standing
> > waves then Q is not a big deal. I believe is is still very very important
> > to use good RF design to reduce parasitic impedances that mess up the
> > primary system and I suspect hurt the quenching. See the paper "Tesla Coil
> > Primary Circuit Behavior Analyzed at High Bandwidth".
In the limited energy system (capacitive discharge), Q merely
reflects losses. One can do measureably better with high Q in both
primary and resonator. I scored a couple of extra inches in that
small system last night by filling the driver with oil to stop the
corona losses.
> > >8. Loaded Fo of system should be < 1/3 resonator Fo with no load
> > > (i.e. capacitive load is =>10X Cint of resonator)
For all intents and purposes, the system is entirely lumped with this
recipe.
> > I have to ask my self "Why doesn't the secondary have standing waves?" and
> > "What about those coils with all the LEDs on them hooked to a signal
> > generator. They seem to show standing wave effects?" Well, I have two
> > theories there.
> >
> > 1. A standing wave system needs a point source to produce standing
> > waves. Thus, our loosely coupled inductive coils have energy being injected
> > into too large of an area to be able to support the point source needed for
> > standing waves. However, a signal generator can inject power at the very
> > base so the standing waves are produced. This implies that "tube" coils and
> > the extra coil in a maggie may have standing waves. However, for energy to
> > be transferred those standing waves must not be maximum, thus these systems
> > work at some VSWR between 1 and some value. (I should have the range
> > covered there :-))
I think one wants high VSWR (Q) to get the high voltages. It will
naturally plummet as output loading increases. IMO, VSWR type theory
has considerably more relevance to CW operation since the energy
source is not finite. A lot has been made of VSWR per se. It pays to
bear in mind that it is related to Q by a simple fixed ratio (4/PI)
so I've never been able to see what the big deal about it is.
> > 2. The dimensions of our coils are too small compared with the
> > wavelength of Fo to set up standing waves. The signal generator driven
> > effect is caused by the distributed capacitance acting with the distributed
> > inductance. Not a standing wave, but more of a distributed impedance effect.
> >
> > If I could determine the base and top current phases of a tube or
> > magnifier coil driven solely at the base, it would answer this question. If
> > they are out of phase, theory #1 is suggested. If they are in phase theory
> > #2 is suggested.
> > There is a way to do this without too much equipment if one can
> > measure the base current. By looking at the phase of the base current and
> > the phase of the top voltage (with an antenna) of a point driven coil, the
> > question can be answered. A coil hooked to a signal generator would work
> > fine. Of course, I can go do that right now and I will
> > :-).................... Well guess what! The base current and top voltage
> > are in phase. That means the base current and top current are 90 out of
> > phase. That means theory number one wins!!! Right on the bleeding edge of
> > science here Dave! Good, I was having a hard time finding a way to explain
> > the details of #2 anyway :-) BTW here is an interesting tidbit. If you
> > have a source and a load impedance with a full standing wave between them,
> > the power delivery to the load is zero! If I had thought that up in the
> > right way years ago this all would have been academic now.... Oh well, when
> > it all falls into place it all comes together at once!
Travelling waves deliver power, standing waves generate voltage.
Interesting post thanks.
Malcolm