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Oudin Coil vs Tesla Coil
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From: Gregory R. Hunter [SMTP:ghunter-at-mail.enterprise-dot-net]
Sent: Saturday, March 21, 1998 2:06 PM
To: Tesla List
Subject: Re: Oudin Coil vs Tesla Coil
> From: Thomas McGahee [SMTP:tom_mcgahee-at-sigmais-dot-com]
> Sent: Friday, March 20, 1998 11:15 AM
> To: Tesla List
> Cc: acmq-at-compuland-dot-com.br
> Subject: Oudin Coil vs Tesla Coil
>
>
> > From: Antonio C. M. de Queiroz [SMTP:acmq-at-compuland-dot-com.br]
> > Sent: Thursday, March 19, 1998 12:40 AM
> > To: Tesla List
> > Subject: Re: Oddball Oudin Coil
> >
> > Gregory R. Hunter wrote:
> >
> > > The device I described in the original post uses the re-wound core and
> > > interrupter from a T-Model induction coil as a kicker. However, the
> > > 75kV business end of the thing is a self-resonant, multi-layered air
> > > core winding excited by a copper tube primary & operating at much
> > > higher frequency than any induction coil. Brent Turner's book has a
> > > good description & schematic of an Oudin coil. If you're interested
> > > in the original article, it's available (scanned) at:
> > > http://www.noah-dot-org/science/x-ray/index.html
> >
> > Note in the circuit diagram (fig. 231) that the primary circuit has a
> > too high series resistance for a Tesla coil (the rheostat), and is
> > -disconnected- from the power source when the current through it is
> > maximum. The input voltage is just 110 V. Too low for a Tesla coil.
> > This is the operation of an induction coil, not a resonant transformer.
> > There is no oscillation (other than parasitic, low Q) in this circuit.
> > What the tube receives is a series of high-voltage pulses, one at each
> > interruption of the primary current.
> >
> > Antonio Carlos M. de Queiroz
> > http://www.coe.ufrj.br/~acmq
> >
>
> Sorry, but the above explanation is not entirely correct. True,
> the Kick Coil itself is indeed a form of self-induction coil.
> Its purpose is to step the 110 volts up to several hundred volts.
> When the Kick Coil pulls in the interrupter there is a fairly
> large peak voltage produced, and this is stored in the capacitor.
> When the interrupter re-connects, it connects the CHARGED capacitor
> to the primary in such a way that it now forms a classic resonant
> circuit. BTW, the official name for that secondary thing is
> "the Resonator". Sound familiar?
>
> The inclusion of the rheostat by Mr. Harry D. Simons was a mistake on
> his part, and when I visited with him in 1965 I pointed out that fact
> to him. He included it simply because he found that it gave him a small
> degree of control over the output. Hey, what works, works!
>
> Tuning this kind of Oudin coil was often done by fiddling around with the
> interrupter mechanism, when in fact it SHOULD have been done by tapping the
> primary. That is how I accomplished it in all the Oudin coils I ever made...
> I ran taps out at each full turn, and one set of quarter taps out at
> the end where the secondary connected to the primary. That allowed me to
> tune within 1/4 turn.
>
> The Oudin coil really *is* a resonant air core system. The type described
> above uses the Kick Coil as the power source, much as we use a neon
> transformer. The spark gap is replaced by the interrupter (which does
> double duty as the Kick Coil vibrator...), and the capacitor, primary
> and secondary are all classic Tesla coil items. For the record, the main
> difference between a classic Tesla coil and a classic Oudin coil is that
> the Oudin coil has one end of the secondary directly connected to one end
> of the primary. That, folks, is truly a minor difference.
>
> The resonant frequency of a multilayer coil tends to be quite low
> by TC standards, but it is still a "resonant" frequency. The
> multilayer Oudin coils can put out a fair amount of useful current.
> The Oudin coil does not "have" to be multilayer. If any of the coilers
> on this list have ever connected the bottom of their secondary
> coils to their primary coil, then they inadvertantly transformed
> their beloved Tesla coil into the much-maligned Oudin coil.
> Shame on you!!! :)
>
> I might add that historically the Oudin coil has been implemented as a
> multi-layer secondary device, but Tesla's early devices also employed
> multiple layers. Tesla often employed the Oudin connection scheme in his
> coils designed for therapeutic applications. So, even Tesla built
> Oudin coils. Oudin just happened to get the patent on this **particular**
> connection scheme. But please, just because the thing is called a Oudin
> coil, let's not assume that it is not "really" a Tesla coil.
>
> Hope this helps.
> Fr. Tom McGahee
>
>
Tom,
Your explanation of the kick coil device was most helpful. I also
appreciate the background info you provided on Oudin coils. However,
your description of the Oudin coil as an end-fed resonator has raised
another question. If the bottom of the resonator winding is
directly connected to the primary tank circuit, then where does the
resonator base current go? Does it become part of the primary
tank current, or what? Is there some other ground path that I've
missed? Just wondering.
Greg
East Anglia, UK