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Re: New System, was "Real Data--



Hi Chuck,
            If you have 0.1uF on hand with some other caps, I would 
love to hear the results of a performance comparison. Sounds like 
you'll need some more primary inductance though.

Malcolm

>     Right now I am trying to sort through several alternatives associated
> with my winter project.  Yes, it is a two coil system and I have a 10
> KVA 14,400 VAC pole pig, welder ballast and Superior 1256D variable
> transformer in the supply.  Last night I decided to change the secondary
> to a 56" length with the 15.25" form diameter in order to get a bit
> lower in frequency.  This results in a resonance of about 106 Khz
> without a toroid.  My curiosity at this point centers about picking the
> optimum capacitor size, with maximum spark being the goal.  I originally
> thought a .1 mfd cap would be about in the correct range, but alot
> depends on how far the secondary resonance will drop with a proper
> toroid, if an ideal L/C ratio is a target.  I'm still not clear on what
> the proper L/C ratio might be.  My 8" diameter by 28" long coil had a
> 221 Khz resonance and with the 48" toroid it dropped to a measured 94
> Khz.  If I could expect the 106 Khz resonance of the new secondary to
> drop to around 50-55 Khz with a big toroid,  I would have a primary
> needing about 100 uh with the .1 mfd cap.  O.K., I guess I could just
> slap a random choice cap size in there and hope for the best, but
> another option makes more sense to me.  That option is, we have a
> tremendous amount of experience in this group and I sure don't mind
> listening for a few weeks and filtering out the stuff that will help me
> get a notch closer to the best I can personally do (The real story is, I
> sure don't want to spend $450-$600 on a cap that isn't quite right!). 
> My last primary had 15 turns so I have no problem with a similar design
> here.  I will use 5/8" thin wall copper refrigeration tube, if they make
> it in that size!  Haven't checked yet.

<snips>