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Re: Primary Q's and Spark Gaps
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To: tesla-at-grendel.objinc-dot-com
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Subject: Re: Primary Q's and Spark Gaps
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From: "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
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Date: Fri, 1 Dec 1995 16:57:59 +1200
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>Received: from rata.vuw.ac.nz (root-at-rata.vuw.ac.nz [130.195.2.11]) by uucp-1.csn-dot-net (8.6.12/8.6.12) with ESMTP id VAA16769 for <tesla-at-grendel.objinc-dot-com>; Thu, 30 Nov 1995 21:00:10 -0700
Hi all,
Written was.....
>
> Just getting back to a topic which bugs me a bit: based on some
> comments by Mark B., I was rather suprised that people are only getting (and
> correct me if this is wrong) primary Q's of maybe 10-20 with no
> coupling to the secondary circuit.
> Throwing some numbers at it, let's assume the primary
> inductances people might use are, say, Lp=100uH and the primary
> capacitance, Cp, might be 20nF. Estimating Qp=sqrt(Lp/Cp)/Rp, the
> "average" primary resistance from all factors such as spark gaps,
> skin, proximity, adn dielectric losses should be about Rp=0.3ohm.
> Seem reasonable?
>
O.K., here are some real figures based on measurement of my coil.
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)
Malcolm