Re: 20 joules at 100 bps vs 4 joules at 500 bps

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 10:13 AM 8/1/2005, Tesla list wrote:
> Original poster: "Dmitry (father dest)" <dest@xxxxxxxxxxx>
>
> Hello Steve.
>
> Tl> Original poster: Steve Conner <steve@xxxxxxxxxxxx>
>
> >>i`ve calculated the toroid voltage (70 cm diameter) - 1.2 MV -
> >>what height should be the secondary to prevent flashovers?
>
> Tl> I believe it should be about 1.2 metres since the breakdown strength
> Tl> of air is 3MV/m and the tracking strength across a surface is roughly
> Tl> one-third of that- 1MV/m.
>
> where did you find that? It`s 3MV/m for DC, but we have HF AC, so this
> value can be several times smaller, 1MV/m - i like it much more :-)


I don't know that the AC breakdown voltage is all that much different 
than the DC breakdown voltage, certainly not factors of 2 or 3 different.

The real aspect to this is that 3MV/m is for a uniform field, and the 
fields around a TC are nowhere near uniform.  The radius of curvature 
of a typical topload is probably in the 5-20 cm range, which would 
imply a breakdown voltage in the 150-600 kV range.  Naturally, if 
your topload isn't nice and smooth (e.g. it's made of corrugated 
aluminum ducting), the breakdown voltage will be MUCH lower.





> http://www.scopeboy.com/tesla/ol2resonator.html
> "The breakout voltage for a 8" x 24" toroid is... something like
> 600kV"
>
> recently Antonio have posted the chart, and according to it breakout
> voltage for this toroid must be equal to 342kv - something wrong here
> :-)

8" = 20cm = 10cm radius.. to a first order 30kV/cm so 300kV would be 
a good guess.

for what it's worth, trying to calculate breakdown voltages to an 
accuracy better than 10% is probably not worth the effort.  In 
precision sphere gaps, the variability from breakdown to breakdown 
with the gap unchanged is in the 5% area.