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Old 5th April 2013, 02:59 PM   #21
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As to ESR, ESR= tan delta/2piifC
Now please explain how could tan delta be improved by much more than a factor of roughly 2 perhaps? 10xsmaller caps against 1x big cap will giv you (neglecting interconnections) roughly half the ESR, add to this the interconnections and you are back at roughly the same ESR that 1 single cap has.

Last edited by gorgon53; 5th April 2013 at 03:08 PM.
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Old 5th April 2013, 03:07 PM   #22
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As I see it, the real advantage of paralleling small caps is the improved MTBF at propable lower costs.
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Old 5th April 2013, 05:38 PM   #23
gootee is offline gootee  United States
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Quote:
Originally Posted by gorgon53 View Post
Hi gootee, and thank you for the link.

Now, Terry made a board of 120x120mm and stuffed it with 100x1000uF caps
of 10-20nH caps. That should giv theoretically a 10-20nH/100=0,1-0,2nH.
He got 1,3nH. It proves that the point I was trying to make holds true
It is a thing of diminishing returns.
No, it proves that he didn't have a thin-enough board on hand, at the time, as he clearly stated. If you read what he said, he calculated that it would be LESS that 0.5 nH.

The equations for paralleling already guarantee diminishing returns. You don't need to claim to be trying to make that point.

Quote:
I would also like to point out that caps of max 12mm diam have to be very low
voltage. Now if you do the same thing with 63-100V caps your board size will increase significantly and so will your inductance. You will end up gettingsometing in the range of at least 3nH. Now compare that to the esl of a otherwise similar single cap with typically 12nH (at most) and you have a improvement of roughly 4. Is that worth the effort? You decide for yourself
Sorry. Your paragraph above is nonsense. You need to learn more, and improve your logic, precision of language, and etiquette, before you again too-casually attempt to cast a pall over other the work of others. It is too fatiguing, for those who might feel obligated, to rebut so many ill-formed arguments at one time.
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Old 5th April 2013, 05:48 PM   #24
gootee is offline gootee  United States
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Quote:
Originally Posted by gorgon53 View Post
As to ESR, ESR= tan delta/2piifC
Now please explain how could tan delta be improved by much more than a factor of roughly 2 perhaps? 10xsmaller caps against 1x big cap will giv you (neglecting interconnections) roughly half the ESR, add to this the interconnections and you are back at roughly the same ESR that 1 single cap has.
No. You explain. Hint: There's more than one capacitor. That ESR(DF) equation is only valid for one cap at a time.

Please show how 10x 1R resistors in parallel have an equivalent resistance of 0.5R, as you claim.
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Old 5th April 2013, 06:26 PM   #25
AndrewT is offline AndrewT  Scotland
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Gootee,
I agree with you, Gorgon has not done his homework and it shows in what he posts.
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regards Andrew T.
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Old 5th April 2013, 07:24 PM   #26
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Andrew
Would you agree that the lowest low-frequency inductance of two very thin conducting planes and having similar but opposing currents flowing forth and being spaced at the minimum distance applied voltages allow, and being at least as wide than long cannot by made any smaller?
If you can agree to that than I suggest you also do your homework and calculate what is the theoretical lowest possible lf-inductance, it will be an eyeopener.
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Old 5th April 2013, 08:26 PM   #27
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Quote:
Originally Posted by gootee View Post
No. You explain. Hint: There's more than one capacitor. That ESR(DF) equation is only valid for one cap at a time. DF is a measure of the deviation from an ideal capacitor. I hope you will realize that the responsible for this deviation is mainly the liquid. So, given the same liquid DF of a small cap in comparsion to a big cap will only be do to minor differences in the metall-conductors and the additonal "fuse" built into big caps (wich givs "appearent" lower losses in the metall conductor-part of the ESR). I say "appereant" because I thinck it is not the best idea to omitt those
in cap-bank capable of really big currents under fault conditions.

Please show how 10x 1R resistors in parallel have an equivalent resistance of 0.5R, as you claim.
This is not what i claim.
For example, 10xRifaPEG124, 1000uf/63V, 100HzESR 90mOhm = 9mOhm,
1xRifaPEH169,10000uF/63V, 100HzESR = 14mOhm.
Smallcap total ESR 9/14= 0,64. If we use a different big cap with ESR of 18mOhm then we get 9/18=0,5. This is what I talked about, I hope you get the picture, not much can be gained in respect to ESR especially since the above neglected interconnection resistances. Add connection R of a dubbelsided
35umCu....I think you get the picture....
As I explained allready, the ESR of a cap is made up of several resistances and the liquid makes up the mainpart of it (as you should be able to see when you look at ESR curves of wet caps). Dissipationfactor for 1 small wet cap does not differ much from the DF of a big wet cap, it is the same liquid.
Anyway, I thinck worth to mention is also the load impedance, the lower the load impence the more you can gain by paralleling. But at 8ohm speaker load
propable not worth the effort as long as you are able to have low RL connections. I do that by using 2 sandwiched 75x 0,2mm copperstripes with
dubblesided gluetape between them. Is flexible and lower R and L than you possible can get otherwise. Next best flexible connection can be made by twisting 2 or more pairs of magnetwire and connect them so currents go back-forth- back a.s.o.
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Old 5th April 2013, 08:58 PM   #28
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Quote:
Originally Posted by gootee View Post
No, it proves that he didn't have a thin-enough board on hand, at the time, as he clearly stated. If you read what he said, he calculated that it would be LESS that 0.5 nH.

The equations for paralleling already guarantee diminishing returns. You don't need to claim to be trying to make that point.



Sorry. Your paragraph above is nonsense. You need to learn more, and improve your logic, precision of language, and etiquette, before you again too-casually attempt to cast a pall over other the work of others. It is too fatiguing, for those who might feel obligated, to rebut so many ill-formed arguments at one time.
gotee, i hope there is no need to be rude, please go into more detail because your outburst does not make much sense to me either
1. Please explain in detail what you think is nonsense
2. where i lack precision and have to improve my logic (always room for improvement for any of us)
3. etiquette ( i have really no idea what this could refere too)
4. many ill-formed arguments at one time (just lets go through them 1 by 1 please)

Last edited by gorgon53; 5th April 2013 at 09:18 PM.
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Old 5th April 2013, 11:05 PM   #29
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Hint, for those of you interrested, Cletus Hoer and Carl Love published in 1965 exact inductance equations for rectangular conductors. The work includes also solutions on how to deal with the impact of nonuniform current distribution

Last edited by gorgon53; 5th April 2013 at 11:10 PM.
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Old 5th April 2013, 11:54 PM   #30
gootee is offline gootee  United States
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Quote:
Originally Posted by gorgon53 View Post
gotee, i hope there is no need to be rude, please go into more detail because your outburst does not make much sense to me either
1. Please explain in detail what you think is nonsense
2. where i lack precision and have to improve my logic (always room for improvement for any of us)
3. etiquette ( i have really no idea what this could refere too)
4. many ill-formed arguments at one time (just lets go through them 1 by 1 please)
No, there was no need to be rude. Sorry. I was aiming at "curt" but not "rude". I was posting from work, which I very-rarely do, and was in too much of a hurry. The reason I was not being as nice as I could have been was that it was somewhat frustrating to see such casual public disagreement with what I considered to be well-established theories, especially since the statements contained what seemed to be errors of fact and logic. I do not usually see the word "proves" used so loosely, for example, in engineering contexts.

At any rate, I think I should ask you to allow me to mostly retract even "curt", for now. I believe that there might have been a bit of misunderstanding on my part, possibly mostly due to communication style and language differences.

Here is your paragraph I was referencing:

Quote:
I would also like to point out that caps of max 12mm diam have to be very low
voltage. Now if you do the same thing with 63-100V caps your board size will increase significantly and so will your inductance. You will end up gettingsometing in the range of at least 3nH. Now compare that to the esl of a otherwise similar single cap with typically 12nH (at most) and you have a improvement of roughly 4. Is that worth the effort? You decide for yourself.
I still disagree, and also believe that most of that is just wrong (which I sometimes call "nonsense").

Sorry but the first sentence instantly struck me as nonsense (especially since my trigger-level was already lowered):

Looking at the Nichicon UHE series electrolytics, in my old Mouser catalog, for example, every voltage rating, from 6.3V to 100V has a 5mm-diameter (or 6.3mm) x 11mm cap. And the 100V ones have a 5mm diameter but the 6.3V ones only go down to 6.3mm diameter.

Maybe you meant to say that C*V had to be low, rather than C, if the diameter was 12mm.

The UHE series only has 12.5mm, not 12mm. The largest (uF) of the 12.5mm diameter models at each voltage rating are 330uF 100V, 680 uF 63V, 1000uF 50V, 1800uF 35V, 2200uF 25V, 3300uF 16V, 4700uF 10V, and 3300uF 6.3V. We would typically be using 35V or 50V caps, maybe 63V, so those values would be 1800uF, 1000uF, and 680uF, which don't seem particularly low.

Also, in every case, where there are two with the same uF and voltage rating, the one with the lower ESR is the one with the lower diameter and greater height. I think you claimed the opposite of that in one or two posts.

Also, as board area increases, inductance would decrease, not increase.

At any rate, the Nichicon UHE series I am looking at only goes up to 1200 uF, in 63V rating. 1200uF has 7.5mm lead spacing. So we could guess its inductance at 7.5L nH (where L is some factor). The 120 uF caps hav 3.5mm LS. So their inductance would probably be close to 3.5L. 10x of them in parallel would give 0.35L. That's 1/21 as much inductance. (I actually have no idea what the inductance would really come out to, in this case. I downloaded an Archambeault paper from the IEEE library, today, at work, but didn't get a chance to look at it, well-enough. It covers the calculation method for exactly this case, and compares calculations to measurements for some examples. But I would need to measure or look up the inductances of the caps, too.)

But even if it was only a 1/4 reduction for a 10/1 increase in number of caps, that would only mean that 10x was not enough caps. We would most likely be in a design situation where we had a target impedance that should not be exceeded over some frequency range. If we needed 57 caps, then that's what we would use (assuming no better way (than caps) was found).
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