First thank you for the help. I'll try to explain my self for this problem and sorry in advance if I'm not very clear, english is not my native language.

I'm making a universal PCB design involving an AC/DC converter. The places where I will install this is in three phase four wire system, three phase three wires systems, and monophasic. Due to this I don't know how to attach my input to the AC/DC converter. I did a research and found that using a three phase may works when you have a three phase three wire systems as I attach next.

Three phase supply

But in this design I'm not using the neutral cable, and if I install this device in a monophasic system won't work at least I connect neutral to L1,L2 or L3. But that won't work for my design purposes. What I would like to achieve is using an universal design that doesn't matter if is 3phase 4 wire or 3phase 3 wires or monophasic. Looking forward, I found this design:

Second design

I understand that the voltage may increase over 564dc or higher, as the source says. But my AC/DC can handle it. My conclusion is that I can use the last design as follow:

My design

Please correct me, I'm wrong.


First design Second design My AC/DC Module

  • \$\begingroup\$ If you need to have the design capable of meeting modern day power factor rules then none of the above will be suitable. \$\endgroup\$
    – Andy aka
    Apr 29, 2020 at 8:21
  • \$\begingroup\$ I do install lots of industrial PSU, Servo Drives,...I had never seen a converter having N,L1,L2,L3 connections. It always L,N or L1, L2, L3. The second holds true even if device is designed to operate mono or three phase, you connect L to L1 and N to L2. The device can't know if you connected the N or L, seems your problem is somwhere else. \$\endgroup\$ Apr 29, 2020 at 20:24
  • \$\begingroup\$ Hi @MarkoBuršič I don't think that it's a problem if the device doesn't know which lines I connected. It just need enough voltage input to work that is what I'm looking for, the main purpose is having an universal PCB design that may fit any electrical wire system. \$\endgroup\$ Apr 30, 2020 at 16:40
  • \$\begingroup\$ Hi @Andyaka thank your for answer. I'm interested in what you said, can you tell more about it? Or any suggested guidelines that I could read? Thank you! \$\endgroup\$ Apr 30, 2020 at 16:43
  • \$\begingroup\$ Vienna 3 phase power factor correction \$\endgroup\$
    – Andy aka
    Apr 30, 2020 at 16:50

1 Answer 1


The power consumption of the RAC05-K/480 is so small that you can take the circuit named "Phase to Phase Application" in your first figure and don't need to worry about unbalacing issues. That would be the simplest solution.

  • \$\begingroup\$ Hi Ken, thank you for answer. Yes it's true I could use it, the issue is that if there is no L1 o L2 I won't work I would like to keep the PCB with the three line traces (L1, L2, L3, N) and doesn't matter the wire system It will continue workin. Even if there is a phase to phase faults and if there are only L1 and N available. \$\endgroup\$ Apr 29, 2020 at 16:38
  • \$\begingroup\$ Your PCB only needs to have two connectors. You either connect L1 and L2 or you connect L and N to these connectors, depending on your network \$\endgroup\$
    – Ken Grimes
    Apr 29, 2020 at 17:20

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