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Conducted emissions issue with multiple Mean Well AC/DC converters
prasimix:
I continued experimenting today by introducing DM choke. First usable case is shown below.
Without load connected on the power modules I got the following:
... and with max. load on two channels it looks like this (I'm on the edge of average limit, but still below quasi-peak limit):
Second usable case include even larger CM choke, 2x11 mH and smaller DM choke (220 uH):
Without connected load:
... and with max. load on two channels:
It seems that DM of about 200 uH and CM of 2x3.3 mH or more is needed. Also X2 on the input has to be 330 nF or more.
I need to find now suitable CM choke rated for 4 A or more since used one is for 2 A only. Another thing that is possible worth trying is two CM filters in series with different characteristics that their leakage inductance is big enough for DM suppression.
A new challenge is to put two chokes (DM+CM or maybe two CM) on the PCB without increasing its dimensions a lot.
TimNJ:
Try putting the choke between two X-caps as Pi filter. Generally, for the same total capacitance (L-C vs. C-L-C) you can get much more attenuation with a Pi filter.
See the below simulation. I've added modest parasitic series inductance and resistance to each element. Using a Pi filter can get you more attenuation or you can get the "same" attenuation as a L-C with smaller components
prasimix:
Excellent suggestion, many thanks! I tried to split existing 430n into two 220n as shown below:
New measurement without load:
... and with max. load:
The final result is comparable with 3 times larger CM choke!
Jay_Diddy_B:
Hi,
You might want to build a DM/CM Separator as I described in this thread:
https://www.eevblog.com/forum/projects/diy-dm-cm-seperator-for-emc-lisn-mate/msg3117396/#msg3117396
If you know if the emissions are CM or DM that you can add the appropriate filtering.
I went to alot of trouble to optimize the performance. But if you just built one, you should get most of the benefits even if the result isn't 100% accurate.
Regards,
Jay_Diddy_B
prasimix:
--- Quote from: Jay_Diddy_B on August 07, 2020, 08:34:30 pm ---Hi,
You might want to build a DM/CM Separator as I described in this thread:
https://www.eevblog.com/forum/projects/diy-dm-cm-seperator-for-emc-lisn-mate/msg3117396/#msg3117396
If you know if the emissions are CM or DM that you can add the appropriate filtering.
I went to alot of trouble to optimize the performance. But if you just built one, you should get most of the benefits even if the result isn't 100% accurate.
Regards,
Jay_Diddy_B
--- End quote ---
Thanks Jay_Diddy_B, I followed that topic, indeed. However, I haven't done anything about it yet because what is left open is what with the cores. Where to get them?
BTW, I tried to treat this issue as CM only and DM only, applying chokes that address one or another mode. But it seems that both of them are very prominent and need to be handled.
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