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Re: Secondary Theory (Was Bipolar Coil)-Heretical view
to: Terry
I wish to point out a slight flaw in paragraph #2. It was never assumed the
electrons travel through the secondary wire anywhere near the speed of
light. Actually, electrons only move several meters per second --- a good
hotrod car can easily outrun them. The wave of energy does travel down the
wire at high velocity.
A mechanical example would be a water wave. Imagine a cork floating
offshore as the waves move inwards. The cork represents the mass of the
electron which bobs vertically while the wave of energy moves through it and
towards the shore at a much higher relative velocity. The cork does
displace and eventually reaches the shore but only after hundreds or
thousands of waves have moved past it. Electron to electron energy transfer
is severly hampered by the inertial mass of the electron. This mass of
course changes depending on whether the electron is more wavelike or
particlelike which depends on the energy in the system. These "initial
conditions" may be modeled with differential equations like the Corums did,
however, they forgot that the initial conditions are not always static (as
you mentioned) in nature --- fractals need to be employed to develop an
effective model of this highly dynamic system.
The wave of energy travels down the wire and is impeded by the wire's
inductance, but another factor enters the equation that plays a far more
significant factor --- the capacitance of each turn of wire (distributed
capacitance) which can rapidly charge and then transmit it's energy through
capacitive reactance at an extremely high velocity. I personally think more
investigation should be done regarding the transfer of energy from turn to
turn as this may be a very significant source of energy transfer along the
secondary coil. These effects would also help to explain some of the rather
weird differences between present theory and practice.
Food for thought.
Regards,
Dr.Resonance
-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Monday, May 17, 1999 7:12 PM
Subject: Re: Secondary Theory (Was Bipolar Coil)-Heretical view
>Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
>
>Hi Jim,
>
> It is very true that using the three lumped parameters (Lsec., Cself, and
>Ctop) will predict Fo, voltages, and currents well. However, the secondary
>system is not just three simple components.
>
> First I'll mention the problems with the old 1/4 wave and wire length
>theory. It was assumed that for electricity to travel the length of the
>secondary, that the electrons would travel through the whole length of the
>wire. Thus, the electrons would flow from the base, to the terminal, and
>back. This is very similar to a 1/4 wave antenna. The resonant frequency
>is simply determined by the time it takes for light to travel the length of
>the wire. This seemed like a reasonable way to determine Fo and explain
>why a bare coil resonates at such a low frequency.
>
> However, there were problems. Medhurst found that an inductor's Fo
>frequency was related to the inductance and dimensions of the coil instead
>of the wire length. Given a coil of a fixed height and diameter, it could
>be shown that a single capacitance could be used to determine Fo along with
>the coils inductance regardless of the length of the wire. The wire
>lengths did not have any correlation and, indeed, it was simple to wind
>coils that violated a simple wire length model.
>
> The next problem was the extreme sensitivity of Fo to external influences.
> If just the wire length were controlling Fo, then simply placing ones hand
>near the coil should not alter the frequency to the extreme degree it does.
> It was obvious that the external fields around the coil were having a very
>profound influence on the resonating system. Medhurst put these two
>together into the Cself of the coil. The coil was now an inductor that had
>a "self capacitance". If you know the inductance and the self capacitance,
>you know Fo. Medhurst did his excellent work and found an empirical
>equation to find Cself based only on coil dimensions. It is well known
>that this equation (the Medhurst equation) can predict the coils Fo
>frequency with remarkable accuracy.
>
> However, there was still a belief that the 1/4 wave model was valid. No
>one really had any reason not to think that the secondary still acted like
>a 1/4 wave antenna instead of a simple inductor in parallel with a
>capacitor. Indeed, the distributed capacitance along the coil fit an
>antenna model better than a lumped model. Problem was, no one could find
>the parameters that would govern this system. The Corums changed that.
>Their "Slow Wave Helical Resonator Theory" adapted transmission line theory
>to the Tesla coil. They used standard transmission line parameters and
>equations to form a model that had distributed components of inductance,
>capacitance, and losses. This model also allowed for 1/4 wave phenomena to
>still exist. However, there was a problem. No one could ever find the
>parameters needed to use the equations. Every coil seemed to have it's own
>parameters. The Corums often sighted the formulas by Kandoian and Sichak
>for finding the transmission line parameters but, in practice, those
>parameters never worked well. A small error would give vastly different
>results. It could also be argued that the use of this empirical formula
>was not appropriate. However, this theory gave a whole new set of
>equations and even introduced the smith chart to Tesla coiling. Sounded
>good, had all the "stuff", based on true electrical engineering theory...
>Just didn't work. They wrote their work up and it was widely distributed.
>Few people really understood both Tesla coils and transmission line theory
>well so the problems were not easy to discover. Most people just read the
>papers, looked at the equations, fearlessly tried to calculate something
>with them, and concluded that it looks great and must be true despite the
>fact that they personally did not have the skills to use the darn thing.
>
> So, you assumed that the Corum's model was correct but used Medhurst to
>find Fo because all that Smith chart stuff was impossible to understand.
>However, many people realized that "something was wrong"...
>
> I am an electrical engineer and I do understand Tesla coils and
>transmission lines. So "no problem"! I'll just click up MathCad, punch in
>the Corum's equations, and I'll be set... Two weeks later, nothing was
>working. The equations gave all kinds of results depending on all kinds of
>things. I started to listen to the "other guys". Malcolm was the first
>person I remember that seemed to have a problem with the 1/4 wave theories.
> It was the coherence theory of the Corum's. Sounded good on paper, but
>was never demonstrated and violated the conservation of energy. Once I saw
>that the Corums could be wrong(!), I started going back and checking
>everything I could. Basically, the 1/4 wave theories didn't work and the
>lumped models did...
>
> The fiber optic probes were coming together about this time (they were
>originally made to study this problem), so I hooked them up to the coil and
>made a bunch of measurements. They were easily able to resolve and measure
>the phase shift from the top to the bottom of the secondary which would
>once and for all determine how much phase shift was going on. The results
>were that there was practically no phase shift! Exactly what the lumped
>models predict! I wrote up the "top and bottom" paper and started the
>"thrash the 1/4 wave theory" thread on this list. For me, the 1/4 wave
>theory fell apart like a house of cards. I was finally able to find the
>"true" transmission line parameters for a coil and it looked like an
>extremely short antenna "stub" with lots of L and C. Resonant yes, 1/4
>wave, not at all... It was like using a 1/4 inch wire in place of a true
>108 inch CB antenna. It was simply far far shorter than needed to support
>1/4 wave effects. It was far closer to a lumped inductor and capacitor
>than a 1/4 wave antenna.
>
> Soooooo... Where are we now...
>
> I now believe that the secondary "can" be modeled as an antenna. A very
>very short one. My coil has a wavelength of a few thousand feet and it
>looks like an antenna 2.5 feet long. It does not transmit well at all.
>There is hardly any phase shift from top to bottom. The reason the wire
>length theory is not valid is because, unlike in a straight wire antenna,
>the windings are all magnetically linked to each other. Current at the
>base of the coil does not need to travel a few thousand feet to reach the
>top. It only has to travel 2.5 feet and magnetically couple to the top. A
>far shorter path and I would submit the "coffin nail" for the 1/4 wave
>theory. The Tesla coil is not a straight wire in free space. It is a coil
>in free space. The current does not travel trough the wire but is induced
>in the coil's turns by magnetic induction. Current in the bottom turn can
>induce current in the top turn in a few nanoseconds. The effects are, for
>all practical purposes, lumped.
>
> The secondary is an inductor, It sits is space and therefor has
>capacitance due to its physical dimensions as any conductor would. Voltage
>on the coil stores charge in this capacitance in the space surrounding the
>secondary. In can do this in a fraction of a nanosecond so the time delays
>are not significant. This capacitance is linked to the coil's turns all
>along the coil's length. This capacitance is distributed in that way, but
>there is practically no time delay involved. Medhurst's equation does
>accurately predict this capacitance given the dimensions of the cylinder.
>When you place a top terminal on a coil, it adds capacitance to the
>structure thus lowering the resonant frequency. The voltage along the
>secondary is distributed as a sine function with the base being at zero
>volts and the top being at full voltage. The current is a "delayed" cosine
>wave. Full current at the base but only maybe 30 of that current is seen
>at the top of the coil. The current divides between the self capacitance
>and the top capacitance.
>
> Wheeler's equations can tell you the inductance of the coil as can any LCR
>meter. There are no significant exceptions there. Medhurst's equations
>can tell you the self capacitance of the inductor also, without exception.
>Fields programs (like my own E-Tesla3) can determine the resonant frequency
>of a coil with a top terminal using the rules in the last paragraph along
>with field theory and Gausses law. It can also generate arrays that show
>the voltage distribution around a given coil. The accuracy is within 5%
>despite the fact that I wrote it :-)) Programs like MicroSim can be used
>to very accurately model Tesla coil systems using lumped parameters
>although it does not show the inner workings of the secondary coil as we
>have discussed.
>
> So, I think we really do know a lot and we are on the right track. Of
>course, that's what Tesla, the Corums, and who knows who else thought...
>The difference is, our ideas seem to work in every situation for everybody.
>
> I do not claim to have "invented" any of this. I may have helped to
>develop some of this or demonstrate something here or there, but many
>people have contributed to all this, not just me. Indeed, I suspect that
>Medhurst could have told us all this long ago....
>
>There is still more to be discovered.....
>
> Terry
>
>
>
>At 09:01 PM 5/16/99 -0700, you wrote:
>>Terry, Malcolm et all,
>>
>> At the risk of sounding ill informed, I'd like to play Devil's
advocate
>>on the 1/4 wave theory. While there is no dispute that lumped parameters
>>"get the job done", perhaps some subtlety has
>>been overlooked. Could the discrepancy between the wire length and actual
>>resonant frequency be a function of velocity? Coil geometry
>>has a great deal to do with the final outcome for many reasons, not
>>the least being distributed capacitance. It sounds reasonable that the
>>more "media" the electrons have to slog through, the slower the velocity.
>>Different combinations of LCR will render the pure length
>>parameter meaningless, yet it still could be a 1/4 wave phenomena.
>>
>> Now that I've braced myself, go ahead and blast me!
>>
>>Jim McVey
>>
>snip..........
>