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Registered Member #3302
Joined: Sun Oct 10 2010, 02:21PM
Location: Finland
Posts: 42
I thought about buying a 500V 3300uF capacitor but i wanted to know if 38mOhm ESR is good or bad compared to other common electrolytic capacitors? I would use it for a coilgun so would it perform well in that usage? I dont need a long answer here, just if its anywhere near the common ESR values that people use in their cap banks.
Registered Member #2906
Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 727
I think its quite a lot of ESR. However, you are able to source 500V.. so you can also have higher losses^^ You should estimate your Coil-ESR, then calculate the maximum current and chek if you will be happy with it. There will be a voltage divider with both ESRs. My 3x 18mF @ 350V in parallel have only 3mOhm ESR... compare it to that^^
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
38 mOhm for 3,300uF 500V is typical for good electrolytics. (for new electroytics, measured esr is usually much lower than specifications) In theory 500V/38mOhm = 13,158 A peak, so if you operate well below this (say <1000 Apk) the esr should not be a problem.
Registered Member #3302
Joined: Sun Oct 10 2010, 02:21PM
Location: Finland
Posts: 42
How about these caps:
1kJ energy for 29€ is what i could afford but are these caps reliable? It says Nippon Chemi-con on the side of the cap in the picture so it should be good quality, but i read the thread here for the 1000J S.C.A.R coilgun and he had some chinese caps fail so do you think these are the same quality as those? Do you know if anyone else has ordered these caps?
I would for sure buy some bigger caps from other countries than China but the shipping costs to Finland are usually bigger than the cap price when ordered from US for example. The chinese sellers have usually free delivery.
Registered Member #3302
Joined: Sun Oct 10 2010, 02:21PM
Location: Finland
Posts: 42
Sorry for double post, but just wanted to say that i won the auction of 3 pieces of 4700uF 450V electrolytic caps. They are used but look like new and work just as they should. The datasheet says their applications include power inverters and circuits with high impulse current so they should be ideal for coilgun and disc launcher purposes :)
I calculated the total energy of them to be 1428J
Here is a link to the datasheet if someone wants to look:
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About capacitor ESR
