Re: Museum Coil Revisited

To: tesla-at-pupman-dot-com
Subject: Re: Museum Coil Revisited
From: Bert Hickman <bert.hickman-at-aquila-dot-com>
Date: Wed, 01 Jan 1997 10:38:36 -0800
Subscriber: bert.hickman-at-aquila-dot-com Wed Jan 1 21:43:31 1997
Tesla List wrote:
> 
> Subscriber: FutureT-at-aol-dot-com Tue Dec 31 22:57:36 1996
> Date: Tue, 31 Dec 1996 15:29:08 -0500
> From: FutureT-at-aol-dot-com
> To: tesla-at-pupman-dot-com
> Subject: Re: Museum Coil Revisited
> 
> In a message dated 96-12-30 19:56:35 EST, you write:
> 
> << > The relatively radical approach used by Cox caused me to take a another
>  > look at this aspect of coil design. It looks like Cox'es grounding
>  > approach may be the best, at least for Museum coils!
>  >
>  > Isn't that the Oudin Coil scheme?
>  >
>  >                                                                 73, Ira
>  >
>  >" Yes, although there's some controversy over just _who_ should be
>  credited with this configuration. There are some who would say that an
>  "Oudin Coil" is also a minor variant of a Tesla Coil, and Oudin should
>  not be credited for what is largely Tesla's work. The reason this
>  configuration is somewhat "radical" today is that it goes against the
>  conventional wisdom on how 2-coil TC's should be constructed from a
>  safety and EMI standpoint, not that it is a brand new approach."
> 
> >Safe coilin' to you, Ira!
> 
>  -- Bert --
>   >>
> I've never used a separate ground for my secondary coil.  I always ground one
> side of my pri. tank, except in neon-sign systems.  I haven't had any
> problems with arcing outlets, etc.  Never gave it too much thought since I
> was busy with other coil aspects, but these posted comments are interesting,
> never realized this hook-up was so rare and disliked.
> 
> I thought also that capacitance between pri. and sec. was to be avoided as an
> operating loss?
> 
>    John Freau

John,

You bring up an interesting point! I had "assumed" that the
configuration of tieing one end of the primary to the secondary was
relatively rare, based upon the excellent design guidelines that Richard
Quick and others have provided on the Tesla site or in previous BBS and
Tesla List postings. I think the main objection was one of safety - with
the primary floating, there was no direct connection between any portion
of the 60 Hz HV, or high-power primary RF section, and the secondary. If
the common connection to ground were to become open or degrade, there
was at least less of a chance that the entire secondary would become
"live" with high voltage at 60 Hz. However, other bad things would
probably happen if you had an open the secondary base ground...
BTW - do you ground the innermost turn or the tapping point?

Primary-Secondary capacitance does not usually operating losses, unless
you're overcoupled and seeing heavy corona breakout between the two.
However, to the extent that higher capacitance effectively increases the
coil self-C or toroid capacitance, it can have the impact of reducing
coil output voltage a bit (all other things remaining the same). Is
there another loss you're thinkning of?

Safe coiling to you!

-- Bert --