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Re: oudin vs. tesla coils

Original poster: "Bert Hickman" <bert.hickman-at-aquila-dot-net> 

Chris and all,

Oudin was a Frenchman who also did HV RF research in Tesla's time. Some
(such as most US scientists) regard his work as being "cloned" from
Tesla's. In reality, it was more likely that Tesla and Oudin were
contemporary, and mostly independent, researchers of RF/resonant
transformers. Certainly the French believe this! :^)

Anyway, the main difference between a Tesla and an Oudin coil is that
the Tesla Coil uses a separate primary and secondary winding and is a
true double-tuned transformer using INDEPENDENT LC circuits. In the
Tesla configuration, the base of the secondary is normally directly
connected to ground. One end of the primary may ALSO be connected to
ground (indeed, some pig coilers run with the innermost portion of the
primary and base of the secondary tied to the same RF ground to reduce
the potential difference between the primary and the secondary
windings). The fact that both the primary and secondary may be tied
together and the common point connected to ground does NOT mean that
this is an Oudin configuration. 

An Oudin coil normally connects ONLY the bottom of the primary to RF
ground. The top of the primary is then connected to the base of the
secondary winding. The base of the secondary is actually connected to
the "hot" end of the primary(!), and the coil operates sort of like a
dual tuned autotransformer, with the secondary resonant circuit sharing
some of the primary circuitry as well. But, this mode of operation is
significantly more dangerous than a Tesla Coil using a common ground
point (above), and is definitely NOT recommended for any high-powered
coils. Oudin DID obtain a patent for this configuration. Tesla also
experimented with it, and this work may have been a step along the way
towards his later magnifier research... 

-- Bert --

Tesla list wrote:
> Original poster: CTCDW-at-aol-dot-com
> Hello folks..
> This might be a long winding post, so hang on :)
> My question is regarding the difference between oudin coils and "pig" powered
> systems which run with one side grounded. By this I mean that one bushing of
> the tfmr is grounded, as are the bases of BOTH the Primary and secondary, as
> well as one side of the spark gap. I have not done much work with my pole
> trfmr coil, as it became obvious that I should just wait to build a proper
> control cabinet. It seems that there is little difference in these systems,
> since in an oudin coil, as far as I have seen, the primary and secondary are
> attatched together, to ground, and to the other bushing of the transformer,
> which effectively grounds one whole side of the  low voltage end of the
> system...
> Is there an electrical explanation of why these are diferent, if indeed they
> are?
> I have heard that an oudin coil uses the primary and secondary as an
> autotransformer, rather than a primary and secondary apart from each other.
> If indeed simply grounding the inner (or bottom) turn of the primary and the
> bottom turn of the secondary together creates an auto transformer, then I
> guess I just learned something :)
> Thanks for any insights!!
> Chris W