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Re: HV xray cable revisited

Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>

Bart,

That's the way that I do it ;^) The capacitance makes the
exterior of the cable "charged" and it can give a little "shock"
if handled energized without the braid being grounded. :^O This
is exactly the way that I feed the power to the base of my
15 kVA "Green Monster" coil system, which can be seen
@: http://dawntreader.net/hvgroup/david/gm.html
The x-ray cables can be clearly seen leading up to the base
of the primary circuit in photo # 22 (I believe), the only spark
shot taken in daylight conditions. I ground the braiding to the
mains ground back at the pole pig's outer tank ground. Works
great with no failures of the insulation running up to around 17
kVAC from the pig when overdriven by a 280 volt input from
the control panel variac.

David Rieben



----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Friday, January 06, 2006 9:17 PM
Subject: Re: HV xray cable revisited



Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>
Hi,
If this is the case, then all those coilers running xray cable should be grounding the braid? It seems the proper method to use this cable would be to sweat back (or strip back) the braid (~ 10") on each end and then ground the braid? 
Take care,
Bart
Tesla list wrote:


Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>

Hi,
The black coating is "resistive" not "conductive". If you ground one end and run say 60Hz AC across it, the far ungrounded end can and probably does get to a pretty high voltage.
For example, if the cable is ten feet long with a resistance of say 10k ohms / foot, then the far end of the cable is 100k ohms to ground. Now if we "assume" a capacitance of 10nF in the cable at 60 Hz we have 265k ohms or leakage reactance to the outer layer. If you put 15kV into the cable, the outer layer voltage is 100k / (265k + 100k) x 15k = 4110 volts. So it arcs to ground very well...
The conductive outer braid was meant to prevent that by providing a solid low resistance conductive path to ground which reduces the outer voltage to very near zero. 

Cheers,

        Terry