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Conducted emissions issue with multiple Mean Well AC/DC converters

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prasimix:
It seems to me that I will not be able to continue testing with the selected filter for the simple reason that the CM choke overheats too much. I overlooked that it was rated for just 1 A :(
The CM choke in question is WE 750314978 and works almost magically, nothing like it in that inductance range (up to 20 mH) filters so well. I don’t know what the trick is, maybe in its high leakage inductance? This is its specification and how it is connected to get results from previous post:




jkostb:
Wurth does has common mode chokes for higher currents. Have you looked at WE-CMBNC series. For example  7448030333 2.5A rated current. You can find a diagram with insertion loss. Frequency range matches with your measurements above. I don't know whether damping is sufficient for your application

https://www.we-online.de/katalog/en/WE-CMBNC?#744803033

TimNJ:
The Wurth choke sems to have a pretty typical leakage inductance for a common-mode choke. 300uH (min) /10mH (typ) = 3% leakage inductance ratio...I think most CMCs are in the range of ~5%, though it can vary considerably with bifilar vs sectional wound. In this case, it's clearly sectional wound with large separation between the windings, so very well may have higher leakage inductance than 300uH.

If that hypothesis is true (that a high leakage inductance is helpful), then that indicates a largely differential-mode issue. It's very convenient to use the leakage inductance of a CMC to achieve adequate DM filtering, but in some cases, you might need a dedicated DM choke. Powdered iron, Sendust, or High-Flux core types is probably what's needed to maintain decent inductance at high current.

prasimix:

--- Quote from: jkostb on August 06, 2020, 05:51:41 pm ---Wurth does has common mode chokes for higher currents. Have you looked at WE-CMBNC series. For example  7448030333 2.5A rated current. You can find a diagram with insertion loss. Frequency range matches with your measurements above. I don't know whether damping is sufficient for your application

https://www.we-online.de/katalog/en/WE-CMBNC?#744803033

--- End quote ---

Actually I did, the following one: 7448030417 that has a much higher inductance (17 mH) and rated for 4 A, but still has a minor effect. I tried few others with inductance about 10 mH but again without notable effect, that is strange.

prasimix:

--- Quote from: TimNJ on August 06, 2020, 05:52:55 pm ---The Wurth choke sems to have a pretty typical leakage inductance for a common-mode choke. 300uH (min) /10mH (typ) = 3% leakage inductance ratio...I think most CMCs are in the range of ~5%, though it can vary considerably with bifilar vs sectional wound. In this case, it's clearly sectional wound with large separation between the windings, so very well may have higher leakage inductance than 300uH.

If that hypothesis is true (that a high leakage inductance is helpful), then that indicates a largely differential-mode issue. It's very convenient to use the leakage inductance of a CMC to achieve adequate DM filtering, but in some cases, you might need a dedicated DM choke. Powdered iron, Sendust, or High-Flux core types is probably what's needed to maintain decent inductance at high current.

--- End quote ---

Yes, it’s one of two planned steps: to add a dedicated DM choke or to take the Mean Well IRM-10 modules out and try something else e.g. RECOM. Cui Inc. has interesting and price attractive modules but it is stated on Mouser that products are available only to OEM/EMS Customers and are not shipped to consumers in the EU.

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