Re: NST failures

["Antonio Carlos M. de Queiroz" <acmq-at-compuland-dot-com.br> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Tesla list wrote:
> 
> Original poster: FutureT-at-aol-dot-com

> In my sync gap coils that use NST power, I always used no more
> than 12" of wiring from NST to tank.  Do you think 12" is within the
> safe limit?  Maybe this is why I've had no failures even when
> running resonant charging with the sync gaps while getting 42"
> sparks from a 12/30 NST, using only safety gaps for protection.
> I wonder if the folks who have had failures were using much
> longer HV leads from the NST?

I think that the observation about capacitive loading in NSTs, really
mentioned on that illustrative web site mentioned, applies only to
installations with -many- meters of wiring. The capacitance that
resonates with the output inductance of a typical NST, as Terry
mentioned, is of several nF at least, and to obtain this capacitance
from simple wires over a grounded surface a very long wire is required.
Just to have an idea, the capacitance of a long wire with
radius a, at a distance h from ground (any unit), h>>a, is:

C = 2*pi*8.85/Ln(d/a) pf/meter

With d=1 cm and a=0.25 mm this results in 14.2 pf/m.
To have 1 nF you must have 70 meters of wire.

Antonio Carlos M. de Queiroz