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Forum Index : Windmills : visual effect of capacitors
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oztules Guru  Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Bob I'm happy to see that you are prepared to follow the truth regardless of the consequences. This leads to a furthering of our understanding that we thought we knew. We will all learn from each other from time to time, having to correct our views on what we had thought had happened to what really may have happened. I won't be backward in trying to uncover the truth..... so much for the pleasantries... down to business. This comment " Oztules comment that non-polarised caps are simply two electrolytics connected back to back is wrong see above. To repeat, the anodising on the film is polarity conscious, reversing the polarity will result in failure." I feel is totally incorrect, and rather than telling you my thoughts, I feel we may as well hear it from the folks who manufacture the things in the first place. First this one from CORNELL DUBILIER...If you didn't know .... it was founded in 1909 by William Dubilier with his invention of the mica capacitor, Cornell Dublier is the oldest capacitor maker in the Western Hemisphere "If two, same-value, aluminum electrolytic capacitors are connected in series, back-to-back with the positive terminals or the negative terminals connected, the resulting single capacitor is a non-polar capacitor with half the capacitance. The two capacitors rectify the applied voltage and act as if they had been bypassed by diodes. When voltage is applied, the correct-polarity capacitor gets the full voltage. In non-polar aluminum electrolytic capacitors and motor-start aluminum electrolytic capacitors a second anode foil substitutes for the cathode foil to achieve a non-polar capacitor in a single case." These are not my words, but theirs. http://www.maelabs.ucsd.edu/mae_es/partsnlinks/PopDataShts/C apacitor%20Application%20Guide.htm If you still feel they are in error, then you can contact them here and tell them why...... 140 Technology Place Liberty, SC 29657 Phone (864) 843-2277, Fax (864) 843-3800 http://www.cornell-dubilier.com E-mail: cde@cornell-dubilier.com 2.184 CORNELL DUBILIER Your Source For Capacitor Solutions Aluminum Application Guide Herb, You may enjoy reading this little gem from Dr Barry Ornitz.... "By the way, electrolytic capacitors act as a conducting diode in reverse polarity. The old electrolytic detectors used by early radio experimenters operated much like electrolytic capacitors. In one direction they conducted; in the other direction they anodized the aluminum electrode". Dr. Barry L. Ornitz WA4VZQ ornitz@tricon.net http://yarchive.net/electr/electrolytic_caps.html But still more understanding can be gleaned from another mauntacturer referenced from Harvard. (This is edited to rid it of some fluff, but the address is below) "Page 1 NICHICON CORPORATION General Descriptions of Aluminum Electolytic Capacitors TECHNICAL NOTES CAT.8101C An aluminum electrolytic capacitor consists of cathode aluminum foil, capacitor paper (electrolytic paper), electrolyte, and an aluminum oxide layer, which acts as the dielectric, formed on the anode foil surface. A very thin oxide layer formed by electrolytic oxidation (formation) offers superior dielectric constant and has rectifying properties. When in contact with electrolyte, the oxide layer possesses an excellent forward direction insulation property. Together with magnified effective surface area attained by etching the foil, a high capacitance yet small sized capacitor becomes available. As previously mentioned, an aluminum electrolytic capacitor is constructed by using two strips of aluminum foil (anode and cathode) with paper interleaved. This foil and paper are then wound into an element and impregnated with electrolyte. The construction of an aluminum electrolytic capacitor is illustrated in Fig. 1-1. Since the oxide layer has rectifying properties, a capacitor has polarity. If both the anode and cathode foils have an oxide layer, the capacitors would be bipolar (non-polar) type capacitor. This can be read in full here: http://209.85.173.132/search?q=cache:SjJZPTot9WIJ:www.nmr.mg h.harvard.edu/~reese/electrolytics/tec1.pdf+ac+electrolytic& hl=en&ct=clnk&cd=58&gl=au No mention is made of protective diodes, but they do mention the diode behavior as used in the wiki, and mine before it. They also don't distinguish between polar and non-polar types as being radically different Herb, I think the manufacturers understand their product enough to give a much better observation of whats actually happening. Bob has not captured at all the intrinsic operation of the caps in this orientation. This quote: "To take this further, the proposed back to back capacitor has 200V across it, which means each series capacitor has 100V. In the middle is a piece of aluminium film, connected to nothing. So what is charged negatively? If these series caps are identical to standard polarised types, then this supposed diode will be easily detectable by testing any electrolytic. Unfortunately nothing can be found, because they don't exist. Go and test one, increase the reverse voltage on a cap and measure the current that flows, it will be an almost straight line. Try it with a diode and it won't be a straight line." This Bob, shows you haven't come to terms with the fact that the electrolyte IS the second terminal. If it were the second aluminum strip, the capacitance would be no better than a paper capacitor. It is only used as a convenient physical charge carrier to cart the charge out of and into your electrolyte/liquid ( ok impregnated paper). In a back to back arrangement, it does not exist in a single can unit....the solution is in contact with itself and both positive plates only. In a separate (two can unit) it is there so we may as well use it to connect the two solutions together... it is not a plate per say. The 100 volts across each cap is a nonsense as well..... each cap sees the entire emf for it's half cycle,... each does not half charge. Each one rises to the full (near too ..dependent on time)) potential, whilst the other is in a state of conduction (shorted out).... other wise the rating would be for twice the voltage.... the manufactures don't support this position. It is true however that running non-polar electros at 100% duty cycle. is not all tea and bikkies Keep the ESR down and the overhead voltage up. It seems big is better (physically) To claim that avoiding self destruction is only due to fortuitous manufacturing is misleading, and does not seem to be supported by the manufacturers themselves.... I don't think it is conspiracy theory either. Sorry about the formatting, but too lazy to change it. Bob, tell your wife that it is all in good spirit, and we aim to learn. I've learnt heaps here, and I have helped from time to time as well.. I hope you will also. I think your current understanding of the mechanics of bipolar operation is plain wrong.... and there is nothing wrong in taking that position, I have taken wrong positions too, but on a forum as robust as this, you will get straightened out eventually... as I have been and are still being. As you can see, I have given the addresses to peruse the full articles, there is another one from Google books that supports my position as well, but I can't cut and paste it I don't think, here is it's address: http://books.google.com.au/books?id=iliZztwXnxAC&pg=PA207&lp g=PA207&dq=ac+electrolytic&source=bl&ots=1XF_HpQ73U&sig=Qow4 1MZ2ok4NViFhQySntZlXgUI&hl=en&sa=X&oi=book_result&resnum=19& ct=result I hope I have given a fair case for ignoring calls for diodes in parallel. They are just not required, and are not mentioned by the manufacturers of back to back caps (read AC electrolytics)..... I truly think you will have to change your perception of caps on this application. I have yet to quantify how the asymmetric leakage does it's thing, and am having difficulty finding decent references to this behavior in caps, but I know I learn't of it somewhere, just have to keep looking. And really it is about time I had a win from Herb. 
..............oztules Village idiot...or... just another hack out of his depth |
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| KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691 |
Thank you Mr Oztules, what you post is extremely enlightening and I have taken the opportunity to reprogramme my memory banks accordingly. I have frequently seen the 'back-to-back' electrolytic 'trick' in various non-professional applications and I have always assumed it was a kluge but apparently I was wrong and that this is acceptable practice. This new knowledge certainly causes me to view that carton of old computer electros in a new light! |
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fillm Guru Joined: 10/02/2007 Location: AustraliaPosts: 730 |
Oztules and to all the "electricial engineers" out there, I will now direct my questions as asked on the bottom of P25 " What direction should I be taking as to DC or AC Caps with regards to testing ? it seems to be leaning towards polarized back to back , how to re-rate them and are there a type that is better to use or can any Vdc Cap be used in my testing in future. As you all know I am more in the field of mechanicial engineering and am having trouble comming up to speed with all this Capacitor Terminology and as I am trying to purchase some different sets of values I dont want to outlay excessive amounts of $ on Caps that will serve no use . PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits |
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| KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691 |
Phill, your testing is in an AC environment so you need AC caps, or you could use pairs of DC caps. If I had to buy them I would be looking for AC caps. Do you know what values (pF) you will be needing? |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Phill, As I have mentioned previously, I am not a fan of using electro's in this configuration, and given a choice would opt for ac caps non-electrolytic. But Thats only because I have had poor cycle life out of the combo's I have used at silly voltages and silly currents. (500uf motor start caps (made from DC back to backs on phase converters for 10hp 3ph motors... but on an island you have no choice.) Used modestly, both Bryan and Gordon have had good life out of their caps so far, and they seem to suffer no unmanageable heating problems.... so It comes down to how hard you push them. I don't recall the ESR rating of their units, but hopefully they will advise you of what they have. I think if you scale it so that you have plenty of current carrying capacity, and they don't heat up markedly, they will last for you. Other uses I have put them too have been altogether too harsh to pass sensible judgment on. Computer power supplies are a good source of HV caps, although Computer monitors have higher voltage ones, as they tend to use flyback style converters, so the supply sees the 340vdc... so they usually have 400vdc caps. The computer ones see half that as they use them in series for predominantly half bridge topologies (so 200v caps).... but should be plentiful and cheap..... just not over here dammit. That will also give you an idea that they don't allow a lot of clearance either... only about 15%. ..........oztules Village idiot...or... just another hack out of his depth |
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| fillm Guru Joined: 10/02/2007 Location: AustraliaPosts: 730 |
"If two, same-value, aluminum electrolytic capacitors are connected in series, back-to-back with the positive terminals or the negative terminals connected, the resulting single capacitor is a non-polar capacitor with half the capacitance.(Quote Oztules last post) Don't know how to use the "Quote" button , I have bought 12 x 470uF 450Vdc caps so if I put two together as neg to neg is the value now 235uF 450Vac and will this handle 130Vac output from the Gen ? I suppose its to late now as I already bought them and will see if they blow up or work .... PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits |
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herbnz Senior Member  Joined: 18/02/2007 Location: New ZealandPosts: 258 |
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Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1344 |
Hi Fillm, Those caps you got are 50 volts higher rating than mine so hopefully they'll work well for you. Cheers Bryan P.S. Oztules I've no idea on the ESR rating of my caps as nothing is written on them. |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Phill, Yes the voltage rating is the same as marked on the caps. Normally series caps would add to 900v ie +-+-, but here we are doing +--+, so each one sees the full potential as the other shorts out... so rating remains at only 450v You will get half the capacitance 230uf or thereabouts... Test with what you have got and monitor the temp... don't let it get into runaway (like Gill, who tested to destruction for us... someone has to ). At 48v, your current comes down to more sensible levels than Gill had to deal with. I suspect you will do fine with your 12 caps. . Provided you don't exceed the 450v,then  . If you exceed even for a very short time, you can punch holes in the oxide layer and well, Bobs predictions will come true. 
Just monitor the temp till you have a feel for it. It wouldn't hurt to wear glasses till your comfortable with the heat dissipation. Don't be frightened, just careful that you can't get hurt, and it can't run away if you have a glitch. (the mill) ............oztules Village idiot...or... just another hack out of his depth |
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GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi oztules, I have had the opportunity to test the diodes as per suggestions. I can say that diodes make no difference to any waveforms on the caps. All the configurations I tested of back to back electrolytic caps give a halving of the capacitance, the same as expected for non polarised varieties. My understanding now is that no matter what, no DC can flow. One cap protects the other. Only Reverse potential DC is the problem I have seen on some caps. If diodes are included, then the minute a cap starts to fail, then this may kill the diode as well, so no benefit. Oztules, your explanation is supported by test results. Hi Bryan, you may have to consult the data sheets for ESR values. I can access a cap ESR meter that TV techs use to test Power supply caps in TV's. Hi Phill, the combination cap will be 235uF NP,450V in the back to back config. The point to note so far with caps, is that Bryan has equivalent 235uF in a series arrangement 24V system, Phill has effectively 2 x 50uF in parallel, in series arrangement, 24V & 48V testing system, I have 1 set of effectively 235uF series arrangement 24V system, and 1 set of 280uF and effectively 2 sets of 165uF in parallel all in parallel series arrangement at 48V system. Two of the above systems are with same type stator, and one is a lower resistance, but the wide range of effective capacitance still seems to work. I doubt the capacitance is really critical. On a separate note, I have tested the output waveform for twisted and non twisted pole fingers On a F&P stator, and I see no difference in the output unloaded voltage waveform, amplitude or shape at the same 200rpm test speed.. Gordon. become more energy aware |
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| fillm Guru Joined: 10/02/2007 Location: AustraliaPosts: 730 |
Hi Gordon, So how low of a uF/Volts value do you think I can go , I came accross a dealer in hong kong who has ac caps used in fans I think , but they are cheap 10uF in 250 and 350Vac and 3.5uF 450vac but they are very compact. I was thinking of testing a set and if they blow put it down to experence.... PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi phill, I have some 11,13,other small values, 240VAC caps. I will make a doubler and series block, and interchange with one of my units. I will get back to you, before you part with your crinkly stuff. Gordon. become more energy aware |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
I have been grappling with the asymmetric leakage angle for a little while, and this appears to be the case. (open for suggestions though) 1. There is slightly more leakage in the reverse biased cap. 2. This leakage charges the forward biased capacitor in the right direction for when the current reverses. 3. Because of the symmetry, each capacitor looks after the other with this asymmetric leakage current. So we should be able to pump the junction up to a bias favorable to the oxide layers. It could be that it is this bias that protects the layer from degradation, and keeps the solution more negative than would have happened if the leakage was symmetrical. If this proves to be correct,then a protecting diode may in fact clamp this protective voltage to a lower value than would be the case without it.... ie it could be that diodes actually place the caps in more peril than without. Conversely, it may also be true that a diode will give it protection for the first few cycles before it builds this bias.  ... or just maybe, without the diode, these leakage effects could repair any junction problems and keep the caps from gradual degradation... pure conjecture on my part.
It is a fact that diodes will stop reverse bias anyway, but I suspect it is more likely to be a case of having a life jacket under you seat when flying over water, than flying without one... it may make you feel safer...but too much current through the ESR will cause you much more pain sooner. It should be possible to measure this and I may do some experiments to see if this can be seen in practice. The fact that the makers of these things don't consider the diodes at all, makes me feel that it is probably better without than with. On a different note. It is commonplace to use bleeder resistors to bleed off the voltage on shut down for safety purposes. These resistors can be placed across the pair only. Nothing must be placed on the center join. On shut down, even if you discharge/bleed the caps "as a unit", there will still be 1/2 potential left in the system. This cannot be bled away using bleeders. It must be left to leak away. Resistors to bleed this away will kill the caps... so make sure you cannot get into contact with the center join, it will have kick left in it. .........oztules Village idiot...or... just another hack out of his depth |
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| woodchips Newbie  Joined: 05/01/2009 Location: United KingdomPosts: 27 |
Hello, and thanks to oztules in particular for all the comments and references. Still don't think we have got to the bottom of this. Following up the references certainly supports oztules points, but if you read further then all the weasel words seems to come in. They all say you mustn't reverse bias the cap because that causes electrolysis of the water creating hydrogen then an explosion. An aside. I did some more general searches on electrolytic caps and I was rather surprised to discover that many different web sites had exactly the same words, the most popular clone was Wikipedia. This is suspicious, people create authoritative web sites by just copying someone else, they don't actually do some original research into the subject. Many years ago I read a book called The Sceptical Environmentalist where someone actually went and looked up the original sources of well known and obviously correct statements about the state of the environment. In an astonishing number of cases this was simply not true, it was all lies and opinion. Read the book and watch your chin bounce off your knees. I had a real example of this in the summer. The British Standards Institute decided trees were dangerous, six people a year were killed by them falling down or branch shedding. We have a wood so this was serious, but after spending weeks hunting down these six deaths I still have no idea where they came from. No names, no places, no dates, no descriptions, almost nothing. The Dubilier application note describes back to back caps and how they work, but later on tells you not to reverse bias them. This is confusing. In the end I could only make sense of it by using the diagram of the back to back caps to introduce the AC electrolytic, they never, or any one else, suggest actually doing this in practise. The discussion then proceeds to how the common centre electrodes are not actually there and both the outer foils have the insulating anodising. They then all go on to say that these caps are not very good, certainly not for 100% duty cycle. They never talk about parallel diodes because I don't think they have ever considered user's would actually connect caps in series, they would buy the proper AC caps instead. There must be real differences between two physical caps back to back and the non-polarised cap. For a start the non-polarised cap has just two foils, so there is no halving of the effective capacitance as seen by the series connection of two caps. Secondly if back to back caps really were switched then the capacitance seen will be the value of one cap, not half. This is because it has just been stated that one cap works, the other is shorted and hence out of circuit. I have done some experimenting, only with low value caps, 33uF, and low voltages, 1 V pk-pk, though. What I have found is that in a series resonant circuit the back to back caps increase the resonant frequency by about 50%, not the 100% expected. More surprising has been that the voltage at the cap centre point can hold a steady DC offset. Once I had nearly 3V but couldn't repeat it. A repeatable offset was about 0.5V positive or negative, depending on how the components were wired. Shorting the cap pulled this offset to zero, removing the offset resulted in the voltage drifting back to where it was. This seemed the same for both caps with and without parallel diodes. Other observations have been the most horrendous noise spikes visible when the capacitor voltage exceeds about 1V in reverse. These were completely suppressed when parallel diodes were fitted. The noise was always on the driving signal form the function generator, which might be an artefact, not certain. There is no clipping of the drive waveform when feeding into just the cap, but there is if there is a parallel diode. Just because oxide rectifiers were used for radio detectors isn't really relevant here, we are operating at power levels a million or more times greater. All I have managed for today, but there is still lots to learn. Bob |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Hi Bob, Skepticism is healthy, and there should be more of it in particular to the environmentalist claims. The DC potential is what i think comes from the asymmetric leakages. I am trying to find out more about it, but I suspect you have found the evidence I was going to look for... and still will. I have heard that it can get up to as high as 16v. Plenty more to learn on this I agree. As always, the proof is in the eating, and some people have had good long term success, so I guess it is fine to as them w/o diodes. I have not done well with AC electrolytics ( NP or back to back polarized)in 100% duty cycle applications over the years, but it has been ESR that has killed them in my applications. Diodes would not have helped.... dry ice may have. Thats all from me for a bit, I have a bulldozer to go and fix .........oztules Village idiot...or... just another hack out of his depth |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Bulldozer and driver doing well... so back to it. Bob, try this one (page 207) previous pages go into finer detail about capacitors in general, with questions etc for their students I assume.. looks like a reasonable read actually... try this one also P207 If you go back over the references, and perhaps the reference at the top of the page, you may note that with back to back caps there is still only two strips and both have oxide coatings. The carrier strips (neg terminal) are not part of the capacitor or it's behavior. Simply ways to connect to the solution.... they are not electrodes in the sense of the word where they take an active roll in the capacitance chemistry. It could be argued that they contribute a tiny fraction of the capacitance as they would be being close wound in a paper capacitor.... but in any meaningful discussion, the "dielectric" thickness for that would be many many orders of magnitude larger than the poly molecular thickness of the oxide layers., For all sensible purposes, it is as the manufacturers indicate... one and the same thing.... however for completeness here it is from them again re: adequacy of foils and definition [quote=Cornell]While it may appear that the capacitance is between the two foils, actually the capacitance is between the anode foil and the electrolyte. The positive plate is the anode foil; the dielectric is the insulating aluminum oxide on the anode foil; the true negative plate is the conductive, liquid electrolyte, and the cathode foil merely connects to the electrolyte. [/quote] [quote=cornell again]In non-polar aluminum electrolytic capacitors and motor-start aluminum electrolytic capacitors a second anode foil substitutes for the cathode foil to achieve a non-polar capacitor in a single case. [/quote] Note the words substitutes for the cathode foil. Now I don't think it is too long a bow to draw to believe that if quote #1 is valid, and the cathode strip plays no part in the capacitor, that when we replace it with and oxide layered strip, the solution is still the electrode, but now sandwiched between the two strips physically. [quote=Bob]For a start the non-polarised cap has just two foils, so there is no halving of the effective capacitance as seen by the series connection of two caps. [/quote] I see no basis for believing that, or any evidence that that may be the case. Think of it this way: We wind a 3 meter oxide foil up and we get 1uf capacitance for a polarized cap... (the cathode is irrelevant to uf... effectively does not exist but to move charge.) We wind a second polarised cap up identically. We now have 6 meters (2uf of oxide) for 2 x 1uf cans.... so .5ufAC NP capacitor Now, we wind another 3m of oxide up for another 1uf, but his time instead of inert 3m of cathode material, we use 3m of oxide material. We now have our NP capacitor using what would have been 2uf of oxide coats (6meters total). They are arranged as two 1uf caps but using the same electrolyte... So instead of sharing the same cathode carrier path.... well they share the same cathode carrier path.... minus the Al foil.. which does not contribute anything of material consequence.... Cornell says so with this " the cathode foil merely connects to the electrolyte."... no more no less.... So,they both look across the same electrolyte, and there are the same two oxide insulating barriers.... just like the two barriers in the two single ones ....so only equivalent to .5uf AC..... if it follows the same rules... and I can't see any difference to reasonably expect them not to... substitute... not in addition too. I am beginning to think this is getting beyond the scope of my abilities to convince you that the manufacturers know what they are talking about. ........oztules Edit... Bob, I have spent further time and effort, but I am (like you) not completely satisfied with the explanations that I have found to date. There are still too many things unknown. I have sent an email to that effect to the technical dept at Cornell, asking for more specific details. whether anything comes of that I don't know, but it is gnawing at my gut that I can't explain sensibly just how this works. All the expert opinions seem to differ from slightly to markedly. (example that link at the top... it is an education text book, but it has different explanations to others...) I am satisfied that the diodes are not necessary, or helpful (in raw terms, they do seem to clean up the reverse bias hash), but I still don't know the real mechanism that is in play ... yet! One thing is certain, there are no diodes in ac caps... I checked. I have opened another thread on a different forum... fishing expedition, you may be interested: here Hopefully we will get to the bottom of this one day. Village idiot...or... just another hack out of his depth |
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MadRat Newbie Joined: 30/09/2008 Location: United StatesPosts: 21 |
I would like to express my thanks for your continued updates on the matter. I'm sure there are many a lurker to this thread that share my opinion. Go Huskers! |
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| woodchips Newbie Joined: 05/01/2009 Location: United KingdomPosts: 27 |
Hello, thanks for the continuing interest. Not much to report, my function generator just doesn't have a high enough output current to actually work the caps, so bit stuck at the moment. Did email Dubilier to ask what they thought, answers will be interesting. I agree with oztules description of the AC cap and how the capacitance is arrived at. Still not clear in my mind about the AC electrolyte. On a polarised cap the negative foil just connects electrically to the electrolyte, fine. On an AC cap all of a sudden it can't connect electrically, there is an insulating oxide film in the way, umm. Get it eventually. Why am I difficult to convince? Manufacturer's write data sheets for their components, giving performance, reliability, operating and other information. All wet electrolytic cap data sheets say the maximum reverse voltage is about 1V. A simple voltage test of back to back caps does not meet this manufacturer's requirement. This was my original comment, clamping the reverse voltage with a diode is necessary. Note that other contributors have reported failures, some quite rapid. Still lots to travel on this one, but hopefully will answer the question once and for all. Bob |
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| KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691 |
Not sure if this is relevant but I dont think the di-electric layer is constant and I recall that on electrolytics that have been standing for some time this layer must be 're-formed' by leaving on a DC voltage for a while, IIRC. |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
I have tested the 450V DC electrolytic caps that Bryan and I are using, rerverse biased to 30VDC. I measured no current on these. Other caps however passed DC when reversed. All DC rated electrolytics are not equal. Gordon. become more energy aware |
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