RE: X-ray HV cables

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Carl Litton" <Carl_Litton@xxxxxxxxxx>


Mike,

Seems like we are talking about the same tape.  The tape is available at
most hardware outlets.  We get it at Home Depot in the electrical
section.  It is a thick spongy rubber tape that has a removable plastic
mesh on one side.

The photo I mentioned last post is here:

http://hvgroup.dawntreader.net/cablestrip.jpg




Carl


-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Sunday, November 06, 2005 12:09 PM
To: tesla@xxxxxxxxxx
Subject: 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.
 >   >   >
 >   >   >
 >   >
 >   >