Re: Primary Q's and Spark Gaps
Subject: Re: Primary Q's and Spark Gaps
From: "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
Date: Tue, 5 Dec 1995 16:05:56 +1200
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Mark Barton writes in response to my post.....
> >Stats : Lp = 11.8uH (including a couple of feet of stray wiring)
> > Cp = 102nF (extended foil)
> > Static Gap firing voltage = 7.5kV
> >Measured Q (using sig gen and scope - i.e. no spark gap) about 50
> > => Rp about 0.22 Ohms
> >Measured Q (operational using ping test and decrement calc.) =11.5
> > => Rtot = 0.95 Ohms
> > => Rgap about 0.73 Ohms!! (accounts for 3/4 of all losses)
> I guess this means your Fo ~= 150KHz. That 0.1uF cap seems a bit large
> for that freq. Tesla ran the Colorado lab at 80-100KHz with 0.12uF.
> You know what to do now. Switch to 0.015uF, about 1/10 what you are
> using now and use a rotary gap. The reactance of the primary
> components will be 80ohms instead of 10ohms. Your Q should go way up,
> tuning get tighter, and (hopefully) sparks get longer.
Hate to disappoint you, but I'm afraid that particular coil's staying
right where it is. I built it for my own interest initially, but they
insisted on paying for it at work, and I no longer treat it as my own
property (i.e. I'm not investing any more time in it). I do have plans
to build a better one at home. I'm particularly keen to see how peak
power scores against average power. Incidentally, I still get better
than 4 feet for 1800W with it. Not the best, but certainly not the
worst. The next coil I build will eclipse it by a mile. I've been
hanging off and hanging off while getting the theory together. Almost
ready, but still one or two things to sus.