Re: X-ray HV cables

["Tesla list" <tesla@xxxxxxxxxx>]

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.
>   >   >
>   >   >
>   >
>   >