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Re: Capacitor Help



Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Malcolm Tesla,

I have long since burned the pictures of my "first" Tesla coil >:o)))))

But now-a-days, the information is soooo much better!!!!

Your coil is looking great!!!

A safety gap is in parallel with the main gap.... There is a long long loooooongg and "very painful" "history" of spark gaps and "resonant cap" systems going "all bad' and blowing up NSTs... A second gap, carefully adjusted, to kick in if the voltage got too much was the standard... But your system could very well do fine without one really...

The concern was that there were decades of info "out there" to use "resonant" cap values that would "ring" the NST voltage "sky high" (like 80kV!!!) if anything went wrong. Thus, one goof, and the NST is fried.... LTR cap values '"fixed that"...

In the transition, super NST protection systems were suggested that would protect the NST against "anything"!!!

http://hot-streamer.com/TeslaCoils/Misc/NSTFilt.jpg

These things worked real real good and decreased the NST killings to almost nill!!! But there is $50 worth of stuff there....

But if you use LTR caps and follow careful suggestions, then things "should be OK". LTR caps will load the NST down enough so that the voltage will not go berserkers... I always worry about people madly trying all kinds of cap values.... Some values are very good, some values are very very bad....

Cheers,

        Terry





At 10:43 PM 12/12/2005, you wrote:
Hey everyone,

Here's a few pics as promised.  This is what I got done over the weekend.
I've since built a little more and done some more wiring.

http://www.v8-ranger.com/temp/tesla/1.jpg
http://www.v8-ranger.com/temp/tesla/2.jpg
http://www.v8-ranger.com/temp/tesla/3.jpg
http://www.v8-ranger.com/temp/tesla/4.jpg
http://www.v8-ranger.com/temp/tesla/5.jpg
http://www.v8-ranger.com/temp/tesla/6.jpg

So as of now I'm going for the MMC with 12 of those 942 caps, and 1 pound of
28 AWG to start winding my secondary.  I have noticed several people mention
a safty gap.  I assume this is about a 1" gap across the capacitor to
prevent any over voltage conditions from blowing the caps?  Like if perhaps
the tesla coil strikes down and hits the primary for example?

Thanks guys, I'll keep you posted
Malcolm

----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Monday, December 12, 2005 10:34 PM
Subject: Re: Capacitor Help


> Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>
>
> Steve, Curt, Malcolm,
>
> Yes, in Malcolm's case, the MMC would certainly be his "best bet".
> However, with large pole pig driven systems,
> a large commercial oil-filled pulse capacitor is actually more
> practical and probably more economical, too. My "Green Monster"
> coil  http://dawntreader.net/hvgroup/david/gm.html uses a .1 uFd
> (100 nFd), 50 kV Hipotronics pulse cap for the primary C and a 15
> kVA, 14,400 volt pole pig. With the variac
> turned up to max, I get 280 volts input and nearly 17 kV
> output from the pig. Although I certainly could build an
> MMC to handle this, it would require say 225 (15 strings
> of 15) of those .1 uFd, 2 kV snubber caps to get a relative-
> ly safe total voltage rating of 30kV at .1 uFd total C. Even at Richard-
> son Electronics' $1.99 each for these, that would still be about
> $450 plus shipping, not to mention the headache of soldering
> 225 individual capacitors (and 225 bleeder resistors) together ;^0
>
> David Rieben
>
> ----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
> To: <tesla@xxxxxxxxxx>
> Sent: Monday, December 12, 2005 4:07 PM
> Subject: Re: Capacitor Help
>
>
> >Original poster: Steve Ward <steve.ward@xxxxxxxxx>
> >I would most certainly disagree here.  An MMC is more robust and gives
> >more "bang for your buck".  Sticking with the CDE 942C series (go to
> >rell.com to order them) you will have no question as to the
> >suitability of the capacitor.
> >Maxwells would be fine if they were new, but in fact most of the
> >maxwells out there (sold by alltronics) were supposedly quite abused
> >in an experiment where they discharged banks of these caps into a
> >spark gap to generate sound to break up kidney stones (dont know if
> >this ever went anywhere).  This is just "word of mouth" stuff, but it
> >seems plausible enough.   Anyway, why not spend less money and get a
> >new capacitor?  Its better than guessing at its suitability and
> >lifetime.
> >For a 15/30 NST, a string of 12 of the .1uF 2kV CDE caps would work (i
> >believe the part number is 942C20P1K.
> >But ouch, it looks like RELL (or CDE) increased the minimum order to
> >~$133.  I believe there was another place that sold CDE caps, Gerry R.
> >mentioned it before.  I think it was:
> >http://mpaqelectronics.com/
> >But it seems like you have to call and ask about them?
> >Good luck.
> >Steve Ward
> >On 12/12/05, Tesla list <tesla@xxxxxxxxxx> wrote:
> > > Original poster: "C. Sibley" <a37chevy@xxxxxxxxx>
> > >
> > > I'd go with a Maxwell pulse capacitor.  The can be had
> > > on e-bay for around $100 and are well worth the $$$.
> > > The have very high peak current and very low
> > > inductance.  If this is your first coil (and not your
> > > last) you will have room to grow as you build more
> > > powerful coils...
> > >
> > > Search e-bay for "Pulse Capacitor" and look for the
> > > big square white block type capacitor.
> > >
> > > Curt.
> > >
> > >
> > > --- Tesla list <tesla@xxxxxxxxxx> wrote:
> > >
> > >  > Original poster: "MalcolmTesla"
> > >  > <tesla@xxxxxxxxxxxxx>
> > >  >
> > >  > Hi everyone,
> > >  >
> > >  > I'm almost done building my first tesla coil.  I
> > >  > used a 15kv 30mA neon sign
> > >  > transformer as my source.  I have a spark gap made
> > >  > with two nuts welded to L
> > >  > shaped brackets with bolts threaded in.  I can
> > >  > adjust the gap by threading
> > >  > the bolts back and forth.  There is a very powerful
> > >  > 110v squirrel cage fan
> > >  > cooling the spark gap.
> > >  >
> > >  > My concern is the capacitor.  I'm trying to purchase
> > >  > something and just not
> > >  > sure what to get.  I've been searching google.com
> > >  > and looking at sites until
> > >  > my eyes can't take it anymore.
> > >  >
> > >  > I can tell from everyone's sites that Polypropylene
> > >  > or Polyethylene is the
> > >  > way to go.  I can get those from mouser.com but they
> > >  > are only 1k to 3k and
> > >  > the just look so darn tiny compare to the pictures I
> > >  > see of everyone else's
> > >  > on the net it's got me worried I'm getting the wrong
> > >  > thing.
> > >  >
> > >  > If anyone can help me out with capacitor values I
> > >  > need, where to purchase,
> > >  > etc. I'd be very grateful.  I did find one at
> > >  > amazing1.com but it was $750.
> > >  > Wow
> > >  >
> > >  > Thanks
> > >  > Malcolm
> > >  >
> > >  >
>
>
>
>
>