[Prev][Next][Index][Thread]
1/4 Wave Theories - Trash Them!
----------
From: Malcolm Watts [SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: Monday, June 01, 1998 5:27 PM
To: Tesla List
Subject: Re: 1/4 Wave Theories - Trash Them!
Hi Terry, all,
> From: terryf-at-verinet-dot-com [SMTP:terryf-at-verinet-dot-com]
> Sent: Thursday, May 28, 1998 1:05 AM
> To: tesla-at-pupman-dot-com
> Subject: 1/4 Wave Theories - Trash Them!
>
> Hi All,
>
> I wrote another paper. What many have suspected, appears to be true.
> Tesla Coils are not antennas. They are transformers.
>
> "An Analysis of Top and Bottom Currents in the Tesla Coil Secondary Inductor."
>
> It can be found as a web page and WORD97 zip at:
>
> http://www.peakpeak-dot-com/~terryf/tesla/experiments/experiments.html
>
> This paper describes measurements of the top and bottom currents in a Tesla
> coil secondary inductor. These measurements indicate that the secondary is
> acting as a simple lumped inductor. There appears to be no 1/4 wave effect.
> The currents are in phase. It appears that the 1/4 wave theory of Tesla
> coil operation is incorrect. Also, the top terminal appears to be acting as
> a simple capacitor in parallel with the coil's self capacitance. A model
> for this behavior is presented.
>
> You can take all those 1/4 wave models and all those books with
> pretty sine wave current distributions and throw them away (Well.... save
> Tesla's)! The basic Tesla coil is a simple lumped parameter transformer
> with loose coupling. Very good news for spice modelers!
>
> Still need to do some theorizing about the self capacitance........
>
>
>
> Now.... comes the sparks!! :-))
>
>
> Terry Fritz
I think there is no doubt this is true when the gap is conducting.
The Corums say this as well. I should point out however that in a
lumped circuit, not only should the phasing criteria be met but the
currents at top and bottom should also be identical as in a closed
circuit (when NO output discharge is issuing). Is this the case? I
suspect not. The Corums say that this is because the coil, being much
shorter physically than the operating wavelength, is immersed in the
primary field. I pointed out to Ken that coupling is virtually non-
existent at the top turns. He pooh-poohed this as incorrect thinking.
Guys and gals, knowing what we now do about magnifiers, I suggest
the lack-of-k-at-the-top argument demonstrably does have merit.
The nub of C&C's argument is that the resonator mode occurs when
the gap has gone out. However, I am sure from my own experiments that
this argument is passe - no-one can put the gap out without a
secondary discharge issuing and without incurring serious losses in
the primary. Besides, when the gap *does* eventually go out, most of
the energy has already disappeared from the system by one route or
another. I still have not seen any magical voltage rise in the
resonator e-field on captured scope waveforms at this time.
The nice thing about the lumped model being valid is that it
does make engineering a system for particular output voltages
possible. One can choose a resonator height with this in mind.
It also ties in nicely with observed single shot spark lengths.
I hate to perpetuate what I think are basically useless ideas
in here but I would be interested to see some top and bottom current
measurements under no breakout conditions. All input welcome.
Malcolm