*To*: Tesla Coil Mailing List <tesla@xxxxxxxxxx>*Subject*: Re: [TCML] Cap and transformer matching: math*From*: Gary Lau <glau1024@xxxxxxxxx>*Date*: Tue, 30 Aug 2016 21:54:21 -0400*Delivered-to*: teslaarchive@xxxxxxxxxx*Delivered-to*: tesla@xxxxxxxxxx*Dkim-signature*: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:reply-to:in-reply-to:references:from:date:message-id :subject:to; bh=NUSF8ITnpW20inorX3zxhZgBjI1+hvRbsPlT5dB/Gsg=; b=zJ3lGJLxcIqwOrKmLKKNGgGiYdID9JIKUjkL3PN00BEmFskpbBEyebQaK3a5v9fGJ/ py+RwSK12zsM1NPgdxTvmwhXOadFI0Jyxd139MkmTvw6TewYuLqish3p2VZ4ekUknBrQ Ujei1kolOwVi++iqhQi23XIP6nQ89IMYcLGUiHtq7tVqql4nzv2z15VjTOsfcg1En+3J XHTSpbolxR3xyd/TMRRKdFO2LVhPZIbVkA0F63a4M7Nta/WW/2s/s0Os9jVH82OhrDuu uQOhI0OqUuqPK1c7jJ1n+1ndjHuVXe+SmUH3ZYPdknvLaPGxop2/FRXrZFvFODoSLiSY skgg==*In-reply-to*: <MWHPR17MB1294158E08A8E349307F3DEED1E00@MWHPR17MB1294.namprd17.prod.outlook.com>*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/options/tesla>, <mailto:tesla-request@pupman.com?subject=unsubscribe>*References*: <2C13D4DA-286B-4ECD-8D87-2D58402AEBC7@gmail.com> <57C2FFFD.4020504@madlabs.info> <MWHPR17MB129499AFA71358C7F21D9D2BD1EE0@MWHPR17MB1294.namprd17.prod.outlook.com> <CAKV84bb8xskgqE3D1g5g0gyQ3HB3oV_svLBuVr_VpSXzDLdrEQ@mail.gmail.com> <MWHPR17MB1294158E08A8E349307F3DEED1E00@MWHPR17MB1294.namprd17.prod.outlook.com>*Reply-to*: Tesla Coil Mailing List <tesla@xxxxxxxxxx>*Sender*: "Tesla" <tesla-bounces@xxxxxxxxxx>

I'm not sure I follow your logic - tau is for R-C circuits, and this is predominantly an L-C circuit. But beyond that, trying to mathematically model an NST charging a cap unfortunately is just not the best approach. NST's become non-linear as the core saturates and no one to my knowledge in the TC community has a satisfactory model to accommodate the non-linear effects, which are extremely significant. The good news is that such core saturation provides a free and welcome boost to the current able to be pulled from an NST, I performed and published a study that measured the actual power processed from a variety of NST's over a range of capacitor values, and the results corroborate the referenced spreadsheet. My report is at: https://drive.google.com/open?id=0B0afsm3K5nFYNGQ3MmJlZGEtYjQ5My00OTJhLTkwNDMtOWEwMjRkYWJkZjAy Regards, Gary Lau MA, USA On Tue, Aug 30, 2016 at 6:08 PM, Brian Hall <brianh4242@xxxxxxxxxxx> wrote: > Thanks Gary and Matt, after reading your replies that does make a lot of > sense now. > > I bookmarked the link for the mmc cap to transformer value table. > > (Please correct me if I'm wrong in the rest of this, but I would like to > make sure I understand what's happening in the circuit). > I actually have a 15/30 NST and the chart tells me that a good LTR value > is 0.0077 uF. > > A cap charges in 5 tau were tau = R times C, and hopefully Resistance in > the tank circuit is low enough to be ignored. > > Thus 0.0077 uF = C = tau, and 5 tau is about 0.0385 microseconds. A full > charge and discharge cap cycle is 10 tau which in this case is 0.077 > microseconds. > > > For a 15/30 NST at 60 Hz, 15kv is actually reached in 1/4 of the sine wave > cycle, in the positive direction, 0 to 90 degrees. The cap discharge also > takes 5 tau were the voltage goes from 15kv to 0v at angles 90 to 180 > degrees as the vector rotates. From 180 to 360 degrees of course the same > thing happens but in the opposite direction of current flow. > > > 60 Hz means that 1/2 cycle occurs in 1/30th of a second = 0.03 seconds. > > Converting to microseconds the decimal is moved six places to the right, > giving us 30,000 microseconds per half cycle. > > This gives us a ratio of 30,000 half cycle microseconds / 0.077 charge and > discharge microseconds (bangs of the spark gap) which is about 389,610 > bangs per half cycle... > > > Where is my math wrong? That really doesn't sound right. > > > ---------------------------------- > Brian Hall > > > > ________________________________ > From: Tesla <tesla-bounces@xxxxxxxxxx> on behalf of Gary Lau < > glau1024@xxxxxxxxx> > Sent: Tuesday, August 30, 2016 5:18 PM > To: Tesla Coil Mailing List > Subject: Re: [TCML] Show and tell first SGTC > > Getting a Tesla coil to operate at peak efficiency is a balancing act > across many parameters. That the primary and secondary circuits are tuned > to roughly the same frequency is the prime directive here, but other things > matter as well. > > The primary cap is not tuned to the NST in a resonant-sense, but it does > need to be "matched", at least in the ballpark, to extract as much power > from the NST as possible. The best way to understand this is to consider > extreme examples. Let's say your NST was a 15/30 and the primary cap was > tiny, say 100pF. Your NST could charge that cap from zero to 15kV in > practically no time. The gap would try to fire hundreds (thousands?) of > times per mains half-cycle, and with the capacitance so low, each "bang" > would have very little energy. This is not what we want - we want there to > be one to a dozen or so as-big-as-possible bangs per half cycle. > > Now consider the other extreme. Let's say your primary cap was huge, let's > say 0.1 uF (one would normally want to use a cap on the order of .006-.01 > uF with a 15/30 NST). With such a too-huge cap, the NST would be unable to > charge the cap to 15kV in a single mains half-cycle. What would actually > happen is that the cap would charge higher and higher on successive > half-cycles until the spark gap breakdown voltage is achieved. You'd get > big bangs, but very infrequently, and it would be murder on your NST. > > There is not a simple formula that one plugs in your NST parameters and out > pops the matched cap value. Instead most coilers use a look-up table that > has proven to be accurate. There are probably other copies floating around > the web - one can be found here: > http://www.classictesla.com/hot-streamer/temp/MMCcapSales.gif > > Regards, Gary Lau > MA, USA > > > > On Sun, Aug 28, 2016 at 7:35 PM, Brian Hall <brianh4242@xxxxxxxxxxx> > wrote: > > > This brings up a general question I have, given what I've read here over > > the years on this list vs. what I have learned about LC resonance in a > > recent college circuit theory class. > > > > If the resonant frequency F = 1/(2pi(sqrt(LC))) then why does the > > capacitance of the primary circuit need to be matched to the transformer? > > > > > > Or is it that the primary capacitor has two attributes: voltage and > > capacitance. The capacitor voltage needs to handle what the transformer > > voltage can deliver, (or 1.5 to 2x the transformer max out volts) and > the > > primary coil L and primary capacitance C need inductive and capacitivie > > values such that F = 1/(2pi(sqrt(LC))) holds true, and match with the > > same resonant frequency F of the secondary LC circuit? Is that all we > > need to change when we swap out a transformer in the primary circuit, > just > > the voltage max on the capacitor? > > > > And Adam, yes I too would like to see a link to the video of your coil, > > always fun to demonstrate your first one! So satisfying to see those > > sparks fly. > > ---------------------------------- > > Brian Hall > > <snip> > _______________________________________________ > Tesla mailing list > Tesla@xxxxxxxxxx > http://www.pupman.com/mailman/listinfo/tesla > > [http://www.classictesla.com/hot-streamer/temp/MMCcapSales.gif] > _______________________________________________ > Tesla mailing list > Tesla@xxxxxxxxxx > http://www.pupman.com/mailman/listinfo/tesla > _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla

**References**:**[TCML] Show and tell first SGTC***From:*Adam Merchant

**Re: [TCML] Show and tell first SGTC***From:*Jonathan Peakall

**Re: [TCML] Show and tell first SGTC***From:*Brian Hall

**Re: [TCML] Show and tell first SGTC***From:*Gary Lau

**Re: [TCML] Cap and transformer matching: math***From:*Brian Hall

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