Hi Bert, Thanks for your reply. I re did my simulation and it seems to support what you said. 1x 1,000uf cap = 84V - 80V/30mS - 656A/30mS 2x 500uF caps = 87V - 85V/30mS - 686A/30mS 4x 250uF caps = 90V - 120V/30mS - 705A/30mS 8x 125uF caps = 90V - 120V/35mS - 713A/30mSThe voltage is the voltage on the cap after the resonant charge cycle, so a slight improvement using parallel caps. Also DVDT seems to make a vast jump with 4 caps. The total amps per discharge improves aswell.
I did not alter the ESR ESL figures, they were kept constant per cap. It seems smaller caps overall have a faster DVDI figure, but ESL & ESR figures seem to be worse overall. that is looking at the DC-Link caps anyway... The 110uF cap is 15nH 4mR, but the 10uF cap is 25nH 7.5mR! So the larger cap has slightly better figures, however they only quote it as 14V/uS and the 10uF cap is 30V/uS, which does not make sense as ESL & ESR figures are worse for the smaller cap.
In this case, after 8 caps there is not much gain and probably no point progressing to 16caps.So it looks like parallel caps is a good thing. Probably not a great deal of gain though it proves an interesting thing!
So far my simulations are pushed for anything over 3V/uS, 5A/uS (18uH primary) So the DC link caps being 14V/uS gives me a little headroom. 10A/uS, 10V/uS with 5uH primary. So even if I progress back down to a smaller primary inductance, then the DC link caps should just about max out at the same point.
The only thing which worrys me a little is that the inductance energy calculation stats 12A flowing in 18uH to equal the input energy.. So the problem with me only pumping 5A would mean over a 50% loss in converting the cap energy into inductance.... Maybe someone on the list can verify that ? Its the problem why I have been stressing over low primary resistance figures and low ESR ESR values... a slight problem somewhere and the design does not function at all...
Like I was saying in my primary thread before, the cap has to discharge via the primary coil, so it has to be low resistnace to lower losses... In fact now I think I realise why I obtain 800V on my primary under simulation.. its not the expected voltage, its the voltage which is probably lost over the primary! which also explains why later simulations it has dropped to 600V....
This is now interesting, I don't know how to work out 1Joule into 18uH exactly, but 1J into 3nF was like 25KV... which I don't know if its correct or not... though I know it welded my test capacitor up, I could only measure 50V on the primary at maybe 10mhz, but it arced together my variable cap.. maybe the voltage on the primary is a lot higher than I think it is.. or even shown on simulation... I don't really know yet!... maybe I should be careful and assume there will be a few KV across my primary just to be on the safe side.....
Cheers, Chris----- Original Message ----- From: "Bert Hickman" <bert.hickman@xxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx> Sent: Friday, August 08, 2008 2:21 PM Subject: Re: [TCML] ESR ESL figures in caps
Hi Chris,In theory, when paralleling N capacitors, overall ESR and ESL will be divided by N (similar to paralleling discrete resistor or inductors). The capacitance will be multiplied by N. So, the equivalent ESR and ESL will be the individual ESR and ESL divided by the number you have in parallel.However, in practice, what you ACTUALLY obtain will be a function of your physical layout and interconnection scheme. For reasonably interconnection schemes, both ESR and ESL will still be significantly lower than that of a single cap, but not as low as theory predicts.Bert -- *************************************************** We specialize in UNIQUE items! Coins shrunk by huge magnetic fields, Lichtenberg Figures (our "Captured Lightning") and out of print technical Books. Visit Stoneridge Engineering at http://www.teslamania.com *************************************************** Chris Swinson wrote:Hi all, I am looking at a cap, 5mR ESR, 15uH ESL.Now if I parallel a load of these, then are the ESR figures multiplied in parallel like regular resistors would add up. For example 10caps 5mR each = 10x5=25mR total ?If I remember right (probably not) , inductors in series multiply, and in parallel half...so Do I have it right in saying ESR figures multiply, and ESL divide ?It could be the total figures may be the same as one cap, though not sure hence the question!I am having problems with simulating this, as going from 1 cap, to 2 caps (half capacitance) they seem to operate different, like one starts to discharge faster, but speeds up as it drops past 50%, and when you swap the caps, the opposite happens, so overall its hard to judge.Cheers! Chris _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla_______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla No virus found in this incoming message.Checked by AVG - http://www.avg.com Version: 8.0.138 / Virus Database: 270.5.12/1599 - Release Date: 07/08/2008 20:49
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