Ripple current rating of Film capacitor in Half Bridge SMPS? - Page 1
Forum section: electronics / general

author: Faringdon
author_rank: Super Contributor
timestamp: January 15, 2022, 09:46:18 pm
content: HiThe attached (LTspice sim and PDF schem) is a 3.6kW Half Bridge SMPS. 3 Phase 240VAC input. 3 phase , 6 pulse rectifier, 12V, 300A output.The Half Bridge primary side rail splitter caps each have 26Arms of ripple current in them.They are as follows…Film capacitor: 12uF MAB MKP 12/400 Siemenshttps://www.rgbautomatyka.pl/media/docs/en/96/12UF%20MAB%20MKP%2012-400%20SIEMENS%20-%20product%20information.pdfHere is a picture of it on ebay...www.ebay.comhttps://www.ebay.com/itm/DVE-EN60252-MAB-MKP-12-400-12UF-5-400V-AC-30000h-Capacitor-New-Quantity-1-/372816438683A proper datasheet cannot be found. (also they dont weigh anything like 1Kg) Do you know how much ripple current they are rated for?

author: Gyro
author_rank: Super Contributor
timestamp: January 17, 2022, 05:48:31 pm
content: How did I guess that this would come round to your 3.6kW half bridge?As I explained in your other thread yesterday...https://www.eevblog.com/forum/beginners/what-is-the-ripple-current-rating-of-this-film-capacitor/, those are bog standard motor run capacitors - they don't specify the figures that you want, specifically, they are rated for 50/60Hz, not 20kHz. Why bother wasting peoples' time if you don't care about the answer!If a figure isn't specified, you can't make use of it. You are asking them to operate at about 20 times the current that they would expect to see!Pleasestop being treez.

author: jonpaul
author_rank: Super Contributor
timestamp: January 17, 2022, 08:54:21 pm
content: Bonjour,Special low ESR high current term film caps are need for high freq high ripple current bridge service.You CANNOT use a 50/60 Hz PFC or motor start cap! Thy will fail.These are not cheap nor readily avail.We used to parallel a bunch of the stacked foil WIMA caps for protosThe US old line cap mfg used to make them, Sangamo, AreoVox, Cornell-Dublier.Am sure the Chinese have cloned these designs.Can send a few photo's if I dig some out of my junkbox.....Kind Regards,Jon

author: Cerebus
author_rank: Super Contributor
timestamp: January 17, 2022, 09:02:33 pm
content: Quote from: mag_therm on January 17, 2022, 08:51:55 pmAs a relative newcomer around here you may be unaware of the 'treez' phenomenon and thus may be misleading yourself. Farringdon (who has been known by a number of user names over the years) often comes looking for free advice for his day job, which is the commercial design and production of power supplies. So there is every possibility that we're not looking, appearances aside, at ahobbyproject here.

author: mag_therm
author_rank: Frequent Contributor
timestamp: January 17, 2022, 09:35:22 pm
content: Thank you,I removed all my posts on the subject.

author: Gyro
author_rank: Super Contributor
timestamp: January 17, 2022, 10:04:53 pm
content: Quote from: Cerebus on January 17, 2022, 09:02:33 pm

author: jonpaul
author_rank: Super Contributor
timestamp: January 18, 2022, 09:36:25 am
content: Rebonjour:CAP ratings: Used low ESR high current film caps in 1970s, like TRW. Mylar and polypropylene film caps with special terminations : AMP connector to all of the foil end layers.WIMA stacked foil polypropylene , MKP4 for pulse application. AM unsure continuous RMS current at high freq.https://www.mouser.com/datasheet/2/440/e_WIMA_MKP_4-1139861.pdfRE "free advice for his day job, which is the commercial design and production of power supplies."I imagined ALL are welcome to EEVblog, to ask for advise regardless of their goal or position: Beginner, hobbyist/DIY, or OEM/professional.Often a professional who seeks assistance has complex, rare and interesting problems and well framed questions.Why not volunteer ones experience if it can help out a fellow engineer or technician?CHEER UP!Have an absolutely fantastic day!Jon

author: Gyro
author_rank: Super Contributor
timestamp: January 18, 2022, 10:23:35 am
content: Quote from: jonpaul on January 18, 2022, 09:36:25 amBonjour Jon,Cerebus's comment doesn't quite cover the extent of the subject. There is alotof history relating to the OP which tends to lead to a certain 'sensitivity' among longer term members. Since his most recent identity change, he does appear to be trying to shrug off his previous reputation, but threads like this, where he proposes using unsuitably rated parts, despite advice from other members (in two threads), tend to act as reminders.Enough said.Chris

author: jonpaul
author_rank: Super Contributor
timestamp: January 18, 2022, 10:54:01 am
content: Dear Chris, mille mercies, I understand totally.As a consultant, I often gave advise which was later ignored.Mr Farringdon's notes are often thought provoking regardless of motive or background.I am happy to share my long experience (a 54 year career) in power electronics, magnetics, high voltage and analog design experienceAny thread and discussion can potentially be of interest to all.Cheers and Bon Journee!Jon

author: Gyro
author_rank: Super Contributor
timestamp: January 19, 2022, 10:26:48 am
content: For educational purposes, a text book example of 'treez behaviour'...https://www.eevblog.com/forum/beginners/what-is-a-motor-capacitor/His third post on motor run capacitors (the second in the Beginners section) to try to obtain a reply from some inexperienced or unsuspecting member, which can be interpreted as what he sees as just enough agreement with his suggestion. He will then use this as a 'justification' for in-product use of the part. He will continue to do this on multiple forums, eg:https://www.edaboard.com/threads/ripple-current-rating-of-film-capacitor.401043/until he gets what he wants, or is reported.If you're really lucky he will soon start another rant about the poor quality of Chinese engineering, and how it's not their fault because we Europeans will buy any rubbish for a low enough price. Ironically, he is designing these product for a Chinese company.

author: jonpaul
author_rank: Super Contributor
timestamp: January 19, 2022, 11:38:05 am
content: Gyro interesting info many thanks!They Chine killed most Western manufacture with the willing aid of US and UK and EU, eg actions of Clintons in 1990s.My businesses have suffered...Bon Journee,Jon