Author Topic: Ripple current rating of Film capacitor in Half Bridge SMPS?  (Read 2130 times)

0 Members and 1 Guest are viewing this topic.

Offline Faringdon

  • Frequent Contributor
  • **
  • Posts: 920
  • Country: gb
Ripple current rating of Film capacitor in Half Bridge SMPS?
« on: January 15, 2022, 09:46:18 pm »
Hi

The 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 Siemens
https://www.rgbautomatyka.pl/media/docs/en/96/12UF%20MAB%20MKP%2012-400%20SIEMENS%20-%20product%20information.pdf

Here is a picture of it on ebay...
www.ebay.com
https://www.ebay.com/itm/DVE-EN60252-MAB-MKP-12-400-12UF-5-400V-AC-30000h-Capacitor-New-Quantity-1-/372816438683

A proper datasheet cannot be found. (also they dont weigh anything like 1Kg) Do you know how much ripple current they are rated for?
« Last Edit: January 15, 2022, 09:47:57 pm by Faringdon »
 

Offline Gyro

  • Super Contributor
  • ***
  • Posts: 7994
  • Country: gb
Re: Ripple current rating of Film capacitor in Half Bridge SMPS?
« Reply #1 on: January 17, 2022, 05:48:31 pm »
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!

Please
stop being treez.
« Last Edit: January 17, 2022, 05:57:53 pm by Gyro »
Regards, Chris

"Victor Meldrew, the Crimson Avenger!"
 
The following users thanked this post: Faringdon

Online jonpaul

  • Super Contributor
  • ***
  • Posts: 1322
  • Country: fr
Re: Ripple current rating of Film capacitor in Half Bridge SMPS?
« Reply #2 on: January 17, 2022, 08:54:21 pm »
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 protos
The 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
Jean-Paul (EE 1968, the Internet Dinosaur)
 
The following users thanked this post: Faringdon

Offline Cerebus

  • Super Contributor
  • ***
  • Posts: 10502
  • Country: gb
Re: Ripple current rating of Film capacitor in Half Bridge SMPS?
« Reply #3 on: January 17, 2022, 09:02:33 pm »
For hobby low power homebrew inverters like this, I would recommend to try to find some snubber capacitors from industrial sized inverters.

As 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 a hobby project here.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 
The following users thanked this post: Gyro, mag_therm, Faringdon

Online mag_therm

  • Frequent Contributor
  • **
  • Posts: 412
  • Country: us
Re: Ripple current rating of Film capacitor in Half Bridge SMPS?
« Reply #4 on: January 17, 2022, 09:35:22 pm »
Thank you,
I removed all my posts on the subject.
 
The following users thanked this post: Faringdon

Offline Gyro

  • Super Contributor
  • ***
  • Posts: 7994
  • Country: gb
Regards, Chris

"Victor Meldrew, the Crimson Avenger!"
 
The following users thanked this post: Faringdon

Online jonpaul

  • Super Contributor
  • ***
  • Posts: 1322
  • Country: fr
Re: Ripple current rating of Film capacitor in Half Bridge SMPS?
« Reply #6 on: January 18, 2022, 09:36:25 am »
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.pdf


RE "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

Jean-Paul (EE 1968, the Internet Dinosaur)
 
The following users thanked this post: Faringdon

Offline Gyro

  • Super Contributor
  • ***
  • Posts: 7994
  • Country: gb
Re: Ripple current rating of Film capacitor in Half Bridge SMPS?
« Reply #7 on: January 18, 2022, 10:23:35 am »
RE "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

Bonjour Jon,

Cerebus's comment doesn't quite cover the extent of the subject. There is a lot of 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
« Last Edit: January 18, 2022, 10:26:04 am by Gyro »
Regards, Chris

"Victor Meldrew, the Crimson Avenger!"
 
The following users thanked this post: Faringdon

Online jonpaul

  • Super Contributor
  • ***
  • Posts: 1322
  • Country: fr
Re: Ripple current rating of Film capacitor in Half Bridge SMPS?
« Reply #8 on: January 18, 2022, 10:54:01 am »
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 experience

Any thread and discussion can  potentially be of interest to all.

Cheers and Bon Journee!

Jon


Jean-Paul (EE 1968, the Internet Dinosaur)
 
The following users thanked this post: SeanB, Gyro, MK14, Faringdon

Offline Gyro

  • Super Contributor
  • ***
  • Posts: 7994
  • Country: gb
Re: Ripple current rating of Film capacitor in Half Bridge SMPS?
« Reply #9 on: January 19, 2022, 10:26:48 am »
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.
« Last Edit: January 19, 2022, 10:49:04 am by Gyro »
Regards, Chris

"Victor Meldrew, the Crimson Avenger!"
 
The following users thanked this post: MK14, Faringdon

Online jonpaul

  • Super Contributor
  • ***
  • Posts: 1322
  • Country: fr
Re: Ripple current rating of Film capacitor in Half Bridge SMPS?
« Reply #10 on: January 19, 2022, 11:38:05 am »
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
 
Jean-Paul (EE 1968, the Internet Dinosaur)
 
The following users thanked this post: Faringdon


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf