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Re: [TCML] New Coil Questions

Hi Tyler,

I think others have already addressed your questions
here but I will just add this little bit about x-ray cable.
High voltage x-ray cables are the lines used to trans-
fer the HVDC and the low filament voltage from the
high voltage transformer supply to the x-ray tube head.
They usually consist of two or three individually insu-
lated (for low voltage) wires (usually around #14 or #
16 braided conductor) in the center. This conductor
bundle is wrapped with a thick layer of rubber insulation,
which is for the high voltage standoff. Around the out-
side of this thick rubber sheathing is usually a wrap of
carbonized semiconductor tape and around the tape is
a metal braided sheating, which is connected to ground.
Finally, around the outside of the metal braiding is a
thin rubber outer protective sleave. Finally, the end
terminations are usually a special male plug end that
fits into the female receptacle ports of the HV transfor-
mer and the x-ray tube heads. Here is a picture of
several rolls of x-ray cable that I recently aquired:

David Rieben

----- Original Message ----- From: "Tyler Pauly" <rpggod714@xxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Wednesday, May 27, 2009 10:20 PM
Subject: Re: [TCML] New Coil Questions

I have more questions on the following two.

7) Can I wire an arc welder in series with my outlet leads to current limit? I would think so, but again, it doesn't hurt to ask.

Yes, a 225 amp stick welder with its 240 input leads in
series with the input leads to the pig can be used as a ballast.
Many people that go this route simply short the output welding
leads and use the amp selector switch for input current control.
However, as Scot has also already mentioned here, most arc
welders are made as cheaply as can be gotten away with and
typically have like a 20% duty cycle at their maximum setting.
I finally ended up making a homemade ballast from the core
of a defunct x-ray transformer. You would have to make sure
that your core has sufficient cross sectional area to handle the
power that you're looking to control, too. Others can comment
on formulae for this.

I've heard of people using a PVC pipe as a form to wind heavy wire around, and sticking welding rods inside to form an inductive ballast. This sounds somewhat cheap and very easy, but will it work? What could go wrong, what should I take into account etc.?

8) My pig only has 1 HV bushing, so should I just split the wiring I attach to it to get 2 leads off of it to make the primary circuit? Sorry for the bad wording, I hope I get my question across.

I also use a "single eared" pig to drive my current big coil with
out any problems. I isolate the case "return" of the pig as RF
ground and do not allow it to be attached to mains ground so
that the nasty RF kickbacks don't end up on the metal
surfaces of my control panel and bite me. ;^0 "I" use
that high voltage rated x-ray cable to run the HV from my
pig to my tank circuit and hook the single output bushing of
the pig to the inner conductors of the cable and the outer tank
to the outer braiding of the cable. This cable is basically coaxi-
al cable on steroids and is generally rated at around 75 kVDC.

I'm a little confused on both responses to this question. For your answer, where do I get some of this cable? And what is the second object I'm connecting the cable to? I'm not very familiar with the lingo used with pigs. So does this cable have two insulated conductors inside? If I were to use normal cable with only one conductor, I would be connecting an end to the bushing and the other end to.... what again? =P

Thanks again!


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