RE: Minimum distance

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>

Guys - I think you're off on the wrong tangent.  The origin question was
asking about any problems with locating one's transformers too close
below the primary, where induced eddy currents from the primary magnetic
field may cause losses in nearby metal objects.  This has nothing to do
with flashover voltages.

My 15/60 NST is mounted roughly 12 inches below my primary.  I'm pleased
with the performance and I've not suffered any trouble related to its
location.  Would the performance be any different if the NST was further
away?  I suspect it would not be measurably different, but truthfully,
I've never tried it and probably won't, as convenience and aesthetics
are more important to me.

Particularly for a relatively low-power system (the poster was talking
about using a 9/30 NST), I wouldn't worry as long as the NST is at least
6-8" away from the primary.

Gary Lau
MA, USA


> Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>
>
> Hi Ben, all,
>
> A 10 kV/inch rule of thumb should prevent almost any
> flashover danger, at least at 60 Hz or DC, as you say.
> However, there are a number variables when determining
> the breakdown distance vs voltage, such as atmospheric
> conditions (temperature, humidity, barometric pressure)
> and the physical size and geometry of the electrodes.
> This makes an "ironclad" voltage/spark length graph all
> but impossible. I think the theoretical maximum voltage standoff that
> 1" of air can withstand is 76 kV, but of course that's with smooth
> spherical electrodes of at least the dia-
> meter of the spark gap distance itself. Any deviation from this
> "controled" laboratory spark gap setup will result in a much lower
> kV/inch rating. I've heard that with needle
> point electrodes, the kV/inch is somewhere between 15
> kV and 25 kV(DC). And of course, with high frequency AC, all bets are
> off as the voltage/spark length ratio goes
> down significantly with a subsequent increase in frequency. Also,
> remember that a 60 Hz AC rms voltage  reading must be multiplied by
> 1.4 to determine the true sine wave peak
> voltage.
>
> David Rieben
>
> ----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
> To: <tesla@xxxxxxxxxx>
> Sent: Wednesday, August 23, 2006 7:52 AM
> Subject: RE: Minimum distance
>
>
> >Original poster: "Bill Miller" <screengrid@xxxxxxxxxxx>
> >Hello,
> >     When dealing with high voltages, I always use the rule of
> > 10,000 volts per inch. Thats at 60 cycles or DC, not sure if it
> > works at other frequencies.
> >Thank You,
> >Tony
> >
> >>From: "Tesla list" <tesla@xxxxxxxxxx>
> >>To: tesla@xxxxxxxxxx
> >>Subject: Minimum distance
> >>Date: Tue, 22 Aug 2006 19:46:05 -0600
> >>
> >>Original poster: "CajunCoiler" <cajuncoiler@xxxxxxxxxxx>
> >>
> >>
> >>The almost-recent talk about transformers below the
> >>primary/secondary coil assembly causing interference
> >>has me pondering...
> >>
> >>...is there a formula for calculating a
> >>minimum non-interfering clearance?  Perhaps even a
> >>"rule of thumb" method?
> >>
> >>I'd like to be able to get placement right the first
> >>time, as financial restraints forbid making changes
> >>to the supporting framework under the supply components
> >>this time around.
> >>
> >>Project parameter data at...
> >>http://www.msbdatasystems.com/cajuncoiler/kongjr.txt
> >>--
> >>C.L. Mayeux
> >>cajuncoiler@xxxxxxxxxxxxxxxxxx
> >
>
>