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Re: Streamer breakout voltages for toroids and spheres
field at the surface of a sphere is = V/r
Streamer breakout occurs when field is greater than breakdown for air, which
is around 31 kV/cm, so a 1 m radius (>6 ft diameter) sphere would
THEORETICALLY breakdown around 3 MV.
HOWEVER, in real life, small bumps cause localized increases in the field
resulting in earlier breakdown. Also, the breakdown for a sphere is
strongly influenced by its surroundings, and any conductor (like the
secondary, or the wire that brings the charge to the sphere, or anything in
the vicinity) will cause a change in the field. Another source of earlier
breakdown is localized electron emission from the surface, as from heating
or UV light.
In general, though, you can figure that the breakdown voltage is roughly
proportional to the radius of curvature.
Toroids are a bit tricky, because the effective radius of curvature is
somewhere between that of the "tube" and the overall radius.
-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Thursday, May 18, 2000 6:29 PM
Subject: Streamer breakout voltages for toroids and spheres
>Original Poster: "Gavin Dingley" <gavin.dingley-at-astra.ukf-dot-net>
>
>Hi all,
>does anyone have a mathematical formula for calculating the voltage
>required for steamer breakout for toroids and sphere isotropic top
>capacities (i.e. a voltage for a given sphere diameter/toroid
>dimensions.
>I was thinking along the lines of calculating the charge density and
>dividing it by the permitivity of free space, then I got stuck!
>
>Thanks in advance for your help,
>
>Regards,
>
>Gavin, U.K.
>
>
>