I have source 400V 50Hz 3 Phase. Each line is 230VAC and maximum current passing by is 10A. This source is connected two motors and one AC/DC converter (24V out) and it is connected to control circuit. For the power part, I used 2.5 mm^2 cable for connection. Everything worked well and now I would like to make it on PCB. However, I don't know how much trace width should I use?

Furthermore, I have no idea what external, internal layer means (I guess it refers multilayer PCBs out and inner layer), I don't know what exactly means temperature rise.

Low current part (control board) I have already made but power part I don't have much idea. I would be glad if someone can help.

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    \$\begingroup\$ I don't know what exactly means temperature rise. - how much hotter something gets compared to ambient. \$\endgroup\$
    – Andy aka
    Commented Feb 15, 2021 at 12:04
  • 1
    \$\begingroup\$ You may also conder using all layers of the board to make parallel connections to reduce the resistance and increase the current. Put the pins as close as possible one to the other. You can use slots for isolation. \$\endgroup\$
    – le_top
    Commented Feb 15, 2021 at 15:41

1 Answer 1


You have two crucial issues here:

  • Current handling (track ampacity) and
  • Insulation (track spacing)

The first one is easy, there are graphs/table to design that. You didn't say how much copper are you using if 35µm or 70µm, this is very important. The relevant standard is IPC-2152 and you can find online calculators using that (a first approximation would be 5mm of width)

The second (arguably more important) is insulation, i.e. spacing (clearance) between traces. You didn't see which overvoltage CAT you circuit is subject to, so it is difficult to say. Usually you want functional insulation between your 400V lines and reinforced insulation between 400V and the low voltage section. There is also another parameter (called creepage) that's an adjustment for the distance. All of this depends also on the environment the board is used in (usually called the 'pollution level'), there are many EN standard covering the requirements. I gave you many keyword to search for.

These are safety features, do not attempt a design if you haven't completely clear the requirements. You do not want your 3-phase supply leaking on your low voltage section. Grounding is critical, too.


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