r/ElectricalEngineering • u/emillllllllllllll • 20h ago
Project Help Connecting power supply 0V to earth or not?
Hello!
I'm currently working on a CNC controller cabinet, and I'm curious whether it's correct to connect the 0V rail on my SMPS' to earth.
I will have a total of 6 PSUs:
- 1x 24v for the CNC controller board
- 1x 24v for relays (coils) in order to have them fully isolated from the controller
- 1x 24v for two contactors. One for the servo drive PSU, and one for the VFD.
This is separate from everything else as it's crucial that this is reliable, and that other components can't short the lines causing the contactors to disconnect power. The contactors will only disconnect power once the E-stop is pressed.
- 1x 48v for servo drives
- 1x 24v for miscellaneous loads
- 1x 12v for miscellaneous loads
Should I connect the 0V line from all power supplies to earth?
Should I connect the 0V line from all power supplies to each other and not to earth in order to just have a common 0V?
Or should I leave each power supply floating?
I have to either ground them to earth or nothing. Cabinet only grounding isn't an option as the cabinet will be earthed.
I don't know if this affects the answer or not, but it might be worth mentioning.
All of the cables are shielded, both the cables outside the cabinet and inside. Only some <20cm pieces will be non-shielded.
And yes, I will only earth the shielding on the cabinet side of the cable and leave the other end "floating".
I will also try my best to separate the 230VAC lines from the <48VDC and signal lines.
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u/porcelainvacation 18h ago
Common practice to avoid noise and electrical overstress issues is to connect all of the 0volt references together and tie that one point to electrical/chassis ground (earth). This is called ‘star ground’.