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Re: [TCML] Looking for Pole Pig Capacitors



On 11/29/2011 9:54 AM, Travis Tabbal wrote:
On Tue, Nov 29, 2011 at 8:17 AM, Roger Smith<rwsmith@xxxxxxxxxxxxxx>  wrote:

Travis,   When I first built my big DC resonant charging Tesla coil I was
using 7200 volt pole pig with a voltage double and I used a 5uF filter
capacitor.  The important thing about your filter capacitor is that it
protects the diodes in your voltage doubler.  If you have a little ripple
in your supply voltage you wont notice it.    One nice thing about about
the voltage doubler is that you can regulate the output by changing the
size of the shifter capacitor.   Most people don't have variacs that can
handle a pole pig system these days.

  As for the voltage doubling effect at the primary capacitor, you don't
have to worry about that.     The same thing goes on with an AC system to
some degree and remember the peak voltage of 14.5 KV transformer is 20.5 KV
  .       I have upgraded from the 7.2 KV  pole pig to a 19.5 KV pole pig
that I am using with a full wave rectifier and a 1 uF filter capacitor and
I haven't blown any capacitors yet and that's running it with 230V going
directly to the pig with no ballasting !      I do believe I'm on thin ice
though.   I haven't put on a lot of run time running it this way.

  As for the deQing diode , I would say you will probably want that .  Some
smaller DC resonant Tesla coils I have built didn't need them but my big
one dose need it.     I haven't done much running with low break rates.
My big coil runs at about 400 breaks per second but on one of the first DC
coils I ever built I got the longest sparks running at a real low break
rate because I had a limited power supply .   It was some kind of a MOT
with voltage doubler arrangement.

Roger


Roger,


Thanks for the great info. So your current system uses a 20KV pig.. So the
coil primary sees 40+KV? No problems with insulation and such at that
voltage? What is your primary cap's voltage rating? For the filter cap, we
don't need anything particular, right? So doorknob caps and such will work?
And I need to rate them for the peak voltage from the transformer, so in my
case running at 14.4KV, 20KV or so. Does the charging inductor need to be
anything particular as far as core material and such?

Come to think of it, I'm sure a lot of my questions would be answered fine
if you have a site documenting your setup?
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Travis, I have quite a mix in my capacitor bank. There are four .04 uF 50 KV Maxwell capacitors in a series parallel arrangement, four .03 uF 35 KV Maxwell capacitors (The same kind Amir is using) in a series parallel arrangement and one .01 uF at 50 KV that I cant remember the brand name of for a total of .08 uF I haven't blown any yet but like I said, I am pushing them a little hard running with a 19.5 KV pig at full power. For filter caps I use oil capacitors. Your best bet might be to get on E bay and look at power factor correction capacitors. They are usually rated in KVARs so you my have to do a little math to find the uF rating.

The main thing about the charging choke is that it has to be able to hold up to the high voltage spikes from the Tesla primary in much the same way as a pole pig dose on a AC system. My charging choke is wound on a big "I" core made from a lot of straight transformer laminations from a big transformer. It has many layers of windings and each layer is insulated from the next with many layers of packaging tape. The inductance is 6 Henerys. I haven't found that the inductance maters much as long as it is enough. Having more than you need won't hurt any thing.

Roger
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