High voltage super capacitors? - Page 1
Forum section: electronics / general

author: najrao
author_rank: Regular Contributor
timestamp: June 26, 2019, 12:42:53 pm
content: Curiosity made me pick up this board from the local flea market. It has 8×1800uF 400V electrolytic caps, arranged for 3600uF 800V with center tap. Also, another six 300uF 350V, similary connected up. There is a bridge rectifier wired as two diodes to charge the biggies in a doubler circuit, ostensibly from 230V a.c. mains. The rest of the circuitry is indecipherable, ic's have obliterated legend.The big caps are 34mm dia× 56 tall, a size in which you normally see about 390uF for a 400V rating. Other than these ratings, there is "RMHCG FA" and 105C written on them.I had never seen so much energy capacity packed into a capacitor of this size.Not much data is found.What possible application?

author: pansku
author_rank: Regular Contributor
timestamp: June 26, 2019, 04:28:54 pm
content: Reminds me of DC link used in variable frequency drives

author: thm_w
author_rank: Super Contributor
timestamp: June 26, 2019, 10:16:16 pm
content: Whats the code above the date? I think it says Y-ZWG120, but no google results for that.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 27, 2019, 12:16:42 am
content: Regular capacitors, nothing super about them. Pictured is about 1kJ of energy, a fair amount as conventional capacitors go but it's about as much energy as a few swings of a hammer!Tim

author: najrao
author_rank: Regular Contributor
timestamp: June 27, 2019, 04:39:11 am
content: Quote from: pansku on June 26, 2019, 04:28:54 pmHave seen such large capacitor banks also inon lineUPS: they also have +and- 400V dc bus, so as to preserve the mains neutral as common to input and output.Quote from: T3sl4co1l on June 27, 2019, 12:16:42 ameffNot too sure, each RMHCG has almost five times the CV*2 as 'normal' caps.Would be interesting to see the specs, ESR, ripple rating, etc. There is some evidence of the manufacturer being Hitachi 'HCA'. There is even a website but this refuses to connect.What would it take a cap to qualify as 'super' ? 36dia×63 has 500F @2.7V; stores 2kJ. Subject is 15% lower volume, and stores 144J. True high voltage caps hold more punch per volume, but 144J?Hope I have not missed zeroes in my calc.

author: BravoV
author_rank: Super Contributor
timestamp: June 27, 2019, 05:06:43 am
content: Not sure, but those RMHCG 1800uF 400V caps look pretty small to me, as relatively compared to TO-220 sized component at the board.Few Epcos and Nippon Chemicon 400V caps I hoarded while ago from industrial PLC power system, shots with TO-220 IC as reference size.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 27, 2019, 05:18:37 am
content: Ah yeah, the size, if they were photoflash style capacitors they might be that small, but it may be they are using "Chinese Farads".Tim

author: tautech
author_rank: Super Contributor
timestamp: June 27, 2019, 05:18:53 am
content: @BravoVYummy !

author: BravoV
author_rank: Super Contributor
timestamp: June 27, 2019, 05:23:17 am
content: Quote from: T3sl4co1l on June 27, 2019, 05:18:37 amWhats the difference photoflash cap vs ordinary one like mine ? Apart from the "Chinese Farads" of course.

author: BravoV
author_rank: Super Contributor
timestamp: June 27, 2019, 05:26:10 am
content: Quote from: tautech on June 27, 2019, 05:18:53 amLOL, thanks, those are impulsive hoard as they're dirt cheap, still dunno what to do with them.Btw, those are pull from used machines in harsh and prolly hot industrial environment, and surprisingly measured with LCR, their capacitance are still above rated capacity.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 27, 2019, 06:00:44 am
content: Quote from: BravoV on June 27, 2019, 05:23:17 amThinner materials resulting in higher ESR, I assume.Conversely, computer grade (screw terminal) caps may not be all that dense. I have a few with embossed sides, which support a smaller roll inside the otherwise oversized case. They may also be made with heavier materials? Dunno.Seems like snap-in style have the best performance, including density (second to photoflash that is), ripple and impedance, in sizes that are large enough to justify their use (since I guess they can't / don't bother to use the construction in say <20mm dia parts, which are only regular leaded style). Like, 1000uF 450V snap-in seems to be better than computer-grade?Tim

author: najrao
author_rank: Regular Contributor
timestamp: June 27, 2019, 07:08:46 am
content: I too have a dozen or so huge 'computer grade' jobs, see comparison to RMHCG.Evil Bay and some Russian websites offer lots of RMHCG. They say 'made in Japan', and mention 'Hitachi aic'. Six smaller 350V 300uF caps on this board (not visible in the photo) are Rubicon. Large hoards of these are offered. There are no grounds to suspect 'chinese farads'.How do they pack so much CV*2 into them?

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 29, 2019, 03:08:29 am
content: Try measuring the actual capacitance. Although I would be a bit surprised if they're fake since that value of high voltage capacitor is generally used where something subpar would more or less not work at all.That board could possibly be out of a studio flash, the voltage seems about right for a large flashbulb.

author: Rerouter
author_rank: Super Contributor
timestamp: June 29, 2019, 03:16:06 am
content: Have a 50L storage tub full of 500V / 2200uF capacitors, They are common in large 3 phase Variable Frequency Drives for the DC rails, there is a point above 4000uF at this voltage that gets too heavy to mount, so they spam them across bus-bars.Found one on the side of the road, and went ham unbolting some 200 odd caps, I just don't have anything interesting to do with them yet.