Do 1,000 Volt electrolytics exist? - Page 1
Forum section: electronics / projects

author: cvanc
author_rank: Frequent Contributor
timestamp: October 08, 2023, 08:51:59 am
content: The highest I've ever seen is 700V, is anyone making thousand volt ones? Thanks.

author: coromonadalix
author_rank: Super Contributor
timestamp: October 08, 2023, 12:22:24 pm
content: https://www.vintage-radio.com/repair-restore-information/valve_capacitors.htmland the one i see in microwaves oven in the 1200 -1500 vdc but they are huge cans ??what is your purpose(s) ?

author: Vovk_Z
author_rank: Super Contributor
timestamp: October 08, 2023, 12:38:45 pm
content: IDK, they might possibly exist, but for real case I would possibly use two 450-500 VDC rated caps in series which are much more easy to buy (if it's for DIY project).

author: tggzzz
author_rank: Super Contributor
timestamp: October 08, 2023, 01:58:24 pm
content: Quote from: cvanc on October 08, 2023, 08:51:59 amQuestion is not interesting unless you state either or both of (1) application (2) capacitance.Without those you will have to be "satisfied" with correct but useless answers such as "put 1000 super capacitors in series, with parallel resistors to ensure the voltage is divided equally".

author: TimFox
author_rank: Super Contributor
timestamp: October 08, 2023, 02:34:37 pm
content: Typical HV supplies for vacuum-tube amateur transmitters use two or three electrolytics in series for 1 kV DC supplies.It is imperative to connect appropriate resistors in parallel with each of the electrolytics to equalize the leakage currents: otherwise, the DC voltage does not divide equally and at least one will see too much voltage.The ARRL handbooks deal with this question.

author: tggzzz
author_rank: Super Contributor
timestamp: October 08, 2023, 03:55:56 pm
content: Quote from: TimFox on October 08, 2023, 02:34:37 pmAdvanced Linear Devices makes some Precision Supercapacitor Auto Balancing (SABTM) MOSFETs.https://www.aldinc.com/pdf/ALD8100xxFamily.pdfThe threshold voltages are factory programmed.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 08, 2023, 04:58:26 pm
content: Aluminum electrolytics top out at 500V or so, for some combination of chemistry and physics of the anodizing process. The oxide layer just doesn't grow further, or alternate breakdown mechanisms occur; I don't know what exactly, but I wouldn't be surprised if there's papers on it.AFAIK, anything higher is series internally. 630V are uncommon but exist, and probably others. I don't know if they use balancing resistors internally.Electrolytics generally balance okay because leakage rises with voltage. What doesn't balance so well is that, when current greater than leakage is delivered over the long term, reforming occurs, gradually increasing the breakdown voltage; as the oxide layer increases, capacitance reduces and foil thickness may be compromised (ESR increases; at some point it goes away entirely and C decreases sharply). (I don't know to what extent which cases happen to an already-500V-rated capacitor.) To avoid this, use a balancing network -- usually just a resistor divider with bias current a few times the maximum expected leakage. If you need low leakage, an active circuit may be necessary.Tim

author: Roehrenonkel
author_rank: Frequent Contributor
timestamp: October 08, 2023, 05:21:08 pm
content: Hi cvanc,no, not that i know.Consider using a foil-cap, much more reliable and safer.And remember: E=0.5*C*U²Good luck

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: October 08, 2023, 06:18:42 pm
content: We used to use 700 VDC axial caps in power supplies where I worked. 8 uF or so if I remember right. One day I cut one open. Yep, two 450 VDC caps in series inside! No resistors because of the self-balancing explanation above. Eventually we just started using two 450 VDC caps, either because it was cheaper or because the 700 VDC ones became hard to get.

author: jonpaul
author_rank: Super Contributor
timestamp: October 09, 2023, 07:08:22 am
content: Most lytics are for SMPS bus at 360V DC, and bridge/rect uses two in series.Broadcast and Hams used several 450V in series with balancing R and C.But no need as oil filled and plastic caps are made to many kV.We have some from Aerovox, at 160 uF and boxes of axial and metal can for 1000...several kV at 1...47 uF.j

author: Haenk
author_rank: Super Contributor
timestamp: October 09, 2023, 12:28:28 pm
content: Röhrenonkel gave a great hint.Looky-look:https://www.ebay.de/itm/1840060389471400DC 1000ACHowever these are PP in Oil, not electrolytic. But likely your only option for higher capacity/voltage.

author: SeanB
author_rank: Super Contributor
timestamp: October 09, 2023, 01:05:55 pm
content: Yes hard to make high voltage electrolytics, probably because of the edges of the foils making a stress concentration. High voltage high capacitance you find film capacitors are the winner, easy to make a thicker plastic dielectric layer, and then wind it into a capacitor using a disposable mandrel, and 2 metallised film layers, to get high voltage, self healing and high capacitance. Then either oil filled, or vacuum epoxy impregnated, to reduce the chances of flash over. Yes the capacitor gets big, but has good pulse handling, and is inherently self healing, and no worries about reverse bias destroying it. But as you rarely need a high capacitance, well worth it. Largest film capacitors I have seen were 100uF 33kV operating voltage, which were heavier than me, and oil filled. Seen some PFC capacitors that are 33kVAR, at 400VAC 3 phase, at the scrap yard, with the value of them being zero, as there is around 10g of aluminium in them over the 2kg of mylar film.

author: Zero999
author_rank: Super Contributor
timestamp: October 11, 2023, 12:11:01 pm
content: Quote from: coromonadalix on October 08, 2023, 12:22:24 pmThose are not electrolytic. They're oil filled.