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Re: X-ray HV cables



Original poster: "MIKE HARDY" <MHARDY@xxxxxxxxxx>

I completely understand now. Just wondering what rubber splicing tape is? I
once had aome rubber-like tape that adhered to itself. So when you wrapped
it upon itself in a spiral, it bonded as one continuous piece after a time
without adhesive.
----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Saturday, November 05, 2005 5:55 PM
Subject: RE: X-ray HV cables


> Original poster: "Carl Litton" <Carl_Litton@xxxxxxxxxx> > > Mike, > > We remove all coverings (outer insulation, braided mesh, and plastic > semi-conducting layer) for the entire length of the stripping (8" in > your case), leaving only the rubber inner core insulation exposed. At > the point 8 inches back where these layers were cut off, we cover the > frayed end of the braided shield and about 2 inches in either direction > with 2 layers of rubber tape followed by a layer of regular plastic > electrical tape. > > I will post some photos of properly prepared cable on the site for you. > > Hope this helps. > > Carl > > > > -----Original Message----- > From: Tesla list [mailto:tesla@xxxxxxxxxx] > Sent: Saturday, November 05, 2005 1:37 PM > To: tesla@xxxxxxxxxx > Subject: Re: X-ray HV cables > > Original poster: "MIKE HARDY" <MHARDY@xxxxxxxxxx> > > > ----- Original Message ----- > From: "Tesla list" <tesla@xxxxxxxxxx> > To: <tesla@xxxxxxxxxx> > Sent: Wednesday, November 02, 2005 2:51 PM > Subject: RE: X-ray HV cables > > > > Original poster: "Carl Litton" <Carl_Litton@xxxxxxxxxx> > > > > Hello Mike, > > > > At lower voltages (below 30 kV), you will be fine if you remove all > > coverings down to the thick rubber layer for 8 " back and then strip > and > > combine the center conductors. We use a few layers of rubber > splicing > > tape followed by electrical tape over the raw ends of the shielding > > material that has been stripped back. The two insulated center > > conductors should have their insulation removed and the strands of > all 3 > > conductors twisted together and soldered. > > > Are you saying cover the entire 'black shield with rubber tape, or just > a > few inches > where it starts? > > > > I am curious about the 150 kV cable and where you obtained it - I > would > > love to get some! Standard x-ray cabling is rated for 75 kV DC and > must > > be derated considerably for AC use. > > > I think other replies to this comment were correct. It's probably 75KV. > I > assumed it was 150 because the max potential on our xray equipment is > 150 KV. > > > We make extensive use of the 75 kV cable in our group projects. At > > higher voltages (100 to 250 kVAC), with the cable laying on the > ground > > and coverings stripped back 18", the current will arc completely > through > > the insulation directly into the ground quite readily, necessitating > > frequent repairs. Up to about 150 kVAC, this may be prevented by > > keeping the cables off of the ground on non-conductive supports. We > > have used it at higher voltages (up to around a quarter Megavolt) by > > running the cable through an outer jacket of heavy wall 1-1/4" I.D. > > vinyl tubing and/or inside of PVC pipe. > > > > We just had to go through all of this for our Halloween Jacob's > Ladder > > running at 215,000 VAC. Here is a not-so-good PowerPoint slide show > of > > it operating at about 175,000 volts using standard 75 kV rated x-ray > > cable prepared as above with 18" stripping on both ends and run > through > > PVC for the greater part of the run: > > > > http://www.dawntreader.net/hvgroup/ladder.ppt > > > > > > Good luck! > > > > > > Carl > > > > > > -----Original Message----- > > From: Tesla list [mailto:tesla@xxxxxxxxxx] > > Sent: Wednesday, November 02, 2005 9:45 AM > > To: tesla@xxxxxxxxxx > > Subject: Re: X-ray HV cables > > > > Original poster: "MIKE HARDY" <MHARDY@xxxxxxxxxx> > > > > I'll answer my own inquiry. On the surface of this remaining HV cable > is > > a > > black hard plastic covering about 0.5 Mil thick. Then about 3/8 " red > > rubber-like insulation, and the center conductors. Seems the black > > plastic > > is what's conductive. I sanded off the black plastic, down to the > red. > > The > > red doesn't conduct. If I remove say 8" of this black coating on each > > end, > > do you think I'll be alright? Will this conductive "shield" cause the > > same > > kind of capacitive resonance problems a true braded shield might. I > > don't > > intend to ground anything, however the cables will be laying on the > > ground. > > ----- Original Message ----- > > From: "Tesla list" <tesla@xxxxxxxxxx> > > To: <tesla@xxxxxxxxxx> > > Sent: Tuesday, November 01, 2005 1:52 PM > > Subject: X-ray HV cables > > > > > > > Original poster: "MIKE HARDY" <MHARDY@xxxxxxxxxx> > > > > > > I got a 150 KV rated xray HV cable. Per D.C.'s recomendations, I > > > stripped the outer jacket, removed the braded shield, and cut off > the > > > 'candlestick' ends. I then reterminated to acomadate the > connections > > > as I needed. The outer jacket (what was under the shield CONDUCTS > !! > > > It nicely shorted the hv output of my PT! What's going on here? > Is > > > this normal? I placed the hv leads of a 15kv nst at 2 points on > the > > > insulation away from the conductor, and it happilly arced! Any > > > thoughts would be apreciated. > > > > > > > > > >