Re: Capacitor Size

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>



Yes ---- a typo.   0.016 uF is correct.

Dr. Resonance



Hi DC:

I assume you meant to say "0.016 at 60 mA".

Have you actually scoped a coil with a static gap
that operates at 120 BPS? Every static gap coil
that I've scoped ran at a far higher rate than
that.  I probably could have achieved 120
(chaotic average) BPS, but I would have had to
open the gap to an unsafe setting.  Since I tend
to use a 2X mains-resonant cap size, I would see
an even higher BPS had I used a 1.57X cap.

In my early naïve days of coiling I thought that
120 BPS was the natural and normal mode of
operation for a static gap.  I know better now
and don't wish to perpetuate that misunderstanding.

Regards, Gary Lau
MA, USA


> Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>
>
>
>
>
> Erms resonant value times 1.57 for best effective C value.  With 30
> mA its near .008 and doubles to 0.16 at 60 mA.  This works best with
> a static copper tube sparkgap firing 120 pps.
>
> Dr. Resonance
>
>
>
>
> >Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>
> >
> >The mains-resonant cap value for a 15/30 NST with 60 Hz power is
> >.0053uF.  It was once thought that this would hit a performance
> >sweet-spot, but I don't think this is so.  Non-linear behavior
> >(ferroresonance) of the NST core makes the mains-resonant cap value a
> >moving target.
> >
> >The rage these days is to use a Larger Than (mains) Resonant cap value.
> >The calculated mains-resonant value multiplied by the square root of 2
> >(or was it 3?) is often cited as the optimum value.  Personally, I've
> >found that 2X the mains-resonant value works well.  I doubt there's any
> >kind of sharp sweet spot, so any of these factors will all work.
> >
> >One thing that is clear is that streamer length is proportional to bang
> >size.  So if your static gap fixes the bang voltage, you can get a
> >bigger bang and longer streamers at a reduced bang interval by using a
> >bigger cap.  But if your wife favors your existing cap, you might get a
> >bigger ba...  OK, I'll stop there.  Always a compromise...
> >
> >Regards, Gary Lau
> >MA, USA
> >
> >
> >
> > > Original poster: "Dirk Stubbs" <dirk@xxxxxxxxxxxxxx>
> > >
> > > I have a question about sizing of a capacitor. My power supply is a
> > > NST 15kV at 30mA. I originally planned on using 10 doorknob
> > > capacitors which are rated at 30kV with 0.006 uF total(each was 620
> > > pF). However I have a question about the needed capacitance for my
> > > TC. Most of the references such as websites  and calculators said
> > > that I need .0053 but I see people saying you need .008-.009 uF.
> > >
> > > What size is correct?
> > >
> > >
> > > What will happen if I use my current capacitor setup?
> > >
> > >
> > >
> > > I would like to use my current setup to save money. The wife has
> > > about had it with the TC as it is . J
> > >
> > >
> > >
> > >
> > > Thanks,
> > > Dirk
> > >
> > > -
> > >
> >
> >
>
>