1/4 Wave Theories - Trash Them!
From: terryf-at-verinet-dot-com [SMTP:terryf-at-verinet-dot-com]
Sent: Wednesday, June 03, 1998 1:46 AM
To: Tesla List
Subject: Re: 1/4 Wave Theories - Trash Them!
At 11:19 PM 6/2/98 -0500, you wrote:
>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
>> It can be found as a web page and WORD97 zip at:
>> This paper describes measurements of the top and bottom currents in a
>> 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.
My measurements WERE without breakout. The gap was quenching early
in the waveforms (30uS) and then the secondary continued to ring after the
gap had stopped conducting. The phase angles on the secondary's top and
bottom remained in phase at all times (during charging and after the gap
quenched). I think the measurements I took are exactly what you want. If
not let me know. I agree with your other comments.