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*To*: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>*Subject*: Re: [TCML] understanding DRSSTC*From*: "Udo Lenz" <udo_lenz@xxxxxxxxxxxxxx>*Date*: Tue, 12 Feb 2013 10:49:41 +0100*Delivered-to*: teslaarchive@xxxxxxxxxx*Delivered-to*: tesla@xxxxxxxxxx*Dkim-signature*: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mx.aol.com; s=20121107; t=1360664130; bh=lsuLdW6nHAUuW70EMs2TPAix3c69KVV/zqpM2OYxzl8=; h=From:To:Subject:Message-ID:Date:MIME-Version:Content-Type; b=wVzP3Eo9QkQZscNkEW9FUnRqB5FgrkjwdSt9VFpO8gkfuNXtCsS9k49y218OYEcqF BzbC31cJF8mu2xIlufP1aN2fyXpb0teooXKWtXiw0PpNCO6oCqB/1om6mEPgaOSlju Q/Ml26+oljQFEDqsP3g6PlwR1Ja4g7ZRQmt+lkgU=*List-archive*: <http://www.pupman.com/pipermail/tesla>*List-help*: <mailto:tesla-request@pupman.com?subject=help>*List-id*: Tesla Coil Mailing List <tesla.pupman.com>*List-post*: <mailto:tesla@pupman.com>*List-subscribe*: <http://www.pupman.com/mailman/listinfo/tesla>, <mailto:tesla-request@pupman.com?subject=subscribe>*List-unsubscribe*: <http://www.pupman.com/mailman/listinfo/tesla>, <mailto:tesla-request@pupman.com?subject=unsubscribe>*References*: <510781E7.22222.26F033@xxxxxxxxxxxxxxxxxxxxx>, <AA15AC9F78E74F4BB90E4A656780F965@UdosLaptop><51175855.6319.ABCD7@xxxxxxxxxxxxxxxxxxxxx> <5117FA4D.9000708@xxxxxxxxx>*Reply-to*: Tesla Coil Mailing List <tesla@xxxxxxxxxx>*Sender*: tesla-bounces@xxxxxxxxxx

Hi Antonio,

I wrote a document with some simulations of a DRSSTC, designed with themethod that I have developed:http://www.coe.ufrj.br/~acmq/tesla/drsstcexcitation.pdfThe simulations show the compromises between operation at the centralfrequency, between thetwo resonances, and operating at the resonances.Operation at the resonances results in excessive primary current andinefficient switching, but you can varythe output power up or down by changing the number of cycles in a burst.Operation at the central frequency results, for a given output voltage,in the smallest possible input current,the fastest possible output voltage rise, and efficient switching.Operation with feedback from the primary current leadsnaturally to this mode of operation, at least with the system designedfor this. The output power canbe varied, but just down, with smaller number of cycles in a burst. Morecycles than the designed maximumdon't necessarily increase the output power in this mode. The designprocedure assumes no load, as donein the design of a classical Tesla coil, but the consideration of aloaded system results in the same conclusions.

The central frequency can be made to match the secondary resonant frequency. If you run at this frequency, the operating frequency will be equal to the secondary frequency and this will give you the highest possible power transfer to the secondary. The pole frequencies can never coincide with the secondary frequency due to the coupling, so that running at their frequencies will require more primary current to achieve a given power transfer.. I believe, this is what you observed. But the central frequency has disadvantages: Consider a simple series tank. If you drive it below the resonant frequency the current phase will lead the input voltage. A PLL circuit would detect that and increase the frequency. The central frequency has the opposite behaviour. There a drop in the frequency leads to a current lagging the voltage. The PLL wouldn't lock on to it. The pole frequencies on the other hand show the "normal" behaviour. You could invert the feedback of the PLL, so that it locks onto the central frequency, but I think, this is a fragile mode of operation, since the inverted phase relation holds only between the poles. A glitch or a ground arc might throw the PLL off. Under heavy arc loading the central frequency will disappear. I believe this to happen at about Qsec = 1/k In your simulation with k=0.12 that would be around Qsec = 8. I've made measurements of arc load at 70kVpeak (at about 200kHz) and they give a load resistance of about 100k. With the parameters you used, Qsec would drop to about 2 with a 100k load. My measurement was made under QCW conditions, so that the arc had time to grow to its final size. With short burst, I'd expect the arc load to be smaller. Nevertheless low Qsecs don't seem to be exotic. Under these conditions you'll have only one ZCS frequency with a "normal" frequency-phase shift relation. An inverted PLL will fail then. Udo _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla

**Follow-Ups**:**Re: [TCML] understanding DRSSTC***From:*Antonio Queiroz

**References**:**Re: [TCML] understanding DRSSTC***From:*Udo Lenz

**Re: [TCML] understanding DRSSTC***From:*Herwig Roscher

**Re: [TCML] understanding DRSSTC***From:*Antonio Queiroz

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