Re: Tesla coil sizes and idea

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

Original poster: Dave Leddon <dave-at-leddon-dot-com> 

At 09:44 AM 9/14/03 -0600, you wrote:
>Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com>
>
>Fat, short coils with efficient design produce good output but tend to arc
>to primary.
>
>Long coils don't intercept the complete magnetic field from the primary and
>loose power transfer.

This begs the question, what is the size and shape of the magnetic field 
produced by a flat Archimedes spiral primary?  I've always assumed that it 
was roughly spherical with a diameter slightly greater than the 
primary.  If that assumption is true then wouldn't that argue for secondary 
winding lengths not much greater than the diameter of the primary?

>4.5:1 height/dia. sec is good aspect ratio for most designs --- even pole
>xmfr designs.
>
>We did a coil once with 3,000 turns --- it didn't outperform our standard
>1,400 turn coil.  Too much resistance.
>
>We tend to standardize everything to 1,400 turns and 4.5:1 for small and
>medium size coils, and use 1,200 turns with 4.5:1 for large, high power
>coils.
>
>These values usually produce a coil with a spark length of 1.25 x the sec.
>winding length.  Values greater than this will breakdown with time unless
>protected by a 4 x sec. dia. toroid.  With our design parameters we use 2:1
>toroid/sec. dia. ratio for most all of our coils.  Good performance with out
>headaches of flashover, etc.  Stability is important in coils running day
>in/day out such as museum applications, etc.
That's a pretty conservative design for non-professional coilers.  I think 
most of us target for arc lengths of at least three times the secondary 
length with long term reliability being less of a concern.

Dave