Re: Source for Aluminum Spheres (up to 12" threaded)

["Tesla list" <tesla-at-pupman-dot-com>]

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

Mike,

Yes. In fact, the E-field stresses may may actually become worse due to 
E-field intensification at the corner (where the dielectric (that houses 
the coil and oil), the output terminal, and the surrounding air all come 
together), called the "triple point". There's simply no substitute for good 
E-field control to prevent initial corona breakout, since once it begins, 
your insulating system's days are numbered.

A simple toroid or graded toroid stack provides superb E-field shielding, 
much greater than a sphere, while also providing excellent design 
flexibility with respect to capacitance, degree of shielding, and  breakout 
voltage. You really don't want to make insulating HV RF more difficult than 
it needs to be.

Granted, a sphere just doesn't look quite as "retro" - anyone remember Dr. 
Zarkov's toys?
Also, see:
http://205.243.100.155/frames/spark-gap.jpg

Best regards,

-- Bert --
-- 
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Tesla list wrote:
>Original poster: "RIAA/MPAA's Worst Nightmare" <mike.marcum-at-zoomtown-dot-com>
>is shading really needed if the secondary is potted transformer oil with the
>sphere sticking out?
>----- Original Message -----
>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: <tesla-at-pupman-dot-com>
>Sent: Tuesday, October 28, 2003 2:38 PM
>Subject: Re: Source for Aluminum Spheres (up to 12" threaded)
>
>  > Original poster: Esondrmn-at-aol-dot-com
>  >
>  > In a message dated 10/25/03 7:11:07 PM Pacific Standard Time,
>  > tesla-at-pupman-dot-com writes:
>  >
>  >
>  > > > In what way better?  Clearly they work just fine but wonder what their
>  > > > edge is over a sphere with the same breakdown voltage.
>  > > >
>  > > > Ed
>  > >
>  > >
>  > >One way I can think of is that a toroid gives you mostly independent
>control
>  > >over the breakout voltage and topload capacitance.  The major diameter
>  > >mostly controls the topload capacitance.  The minor diameter mostly
>controls
>  > >the breakout voltage.  With a sphere, you don't have this level of
>control.
>  > >
>  > >Gerry R
>  > >Ft Collins, CO
>  >
>  >
>  > Also, the toroid will provide "shading" for the top few windings of the
>  > coil so we don't get sparks breaking out from there.  I have tried spheres
>  > on my three inch secondary and still had to have a small toroid on top
>then
>  > the sphere raised up from there.
>  >
>  > Ed Sonderman
>  >
>  >
>
>.