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I'm designing, for a railways application, the power supply circuit on a pcb board that supply 5Vdc starting from a 24Vdc(coming from a not clearly defined source, sure a 24Vdc line).

I'm using the TRACOPOWER TEN 40WIR isolated DC/DC converter(railways compliance): (https://www.tracopower.com/products/ten40wir.pdf)

My questions concern the EMI filter circuit. I'm reading the application note from Tracopower (ten40wir-emc-consideration from Traco website) where I find this figure with suggested filter to comply EN50155 Immunity: enter image description here

Can someone help me, giving me indications on how to design and size an EMI filter that satisfies the en50155?

Maybe there is a commercial solution that is suitable for railways use?

Thanks you

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  • \$\begingroup\$ A quick check suggests, that 50155 is about surge and transient immunity. Your average conducted emission EMI filter does not help against that. It is just left in as a block in the TRACO diagram, to suggest that you still need this block, but it plays basically no role in the 50155. \$\endgroup\$
    – tobalt
    Nov 15, 2021 at 13:10

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Your EMI link includes 3 pdf files which identify how to layout the PCB and select the inductor and size the capacitors.

https://assets.tracopower.com/20191122153555/TEN40WIR/documents/ten40wir-application.zip

If you ask for the version with F added to suffix , they can make or find stock to include filter.

Suffix -CMF

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  • \$\begingroup\$ So, I can use the suggested filter on page 1 (for example) and put it in the EMI FILTER black box. Unfortunately, it seems that there is no possibility to request the device I chose (TEN 40WIR 2411) with the emi filter inside ( and obviously, the filtered model costs a lot). \$\endgroup\$
    – Cataldo
    Nov 25, 2019 at 9:06
  • \$\begingroup\$ If the factory cannot make the PCB, then demand is too low. So you must ask them or yourself for a make/buy ROI calculation \$\endgroup\$ Nov 25, 2019 at 13:35

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