How to connect PCU to Stepper driver (NEMA 23)
The A/C (input) side of your supply is Earth, Neutral, and Line.  The D/C  (output) side is V+ and V-.  For the D/C side you usually use the V- as &quot;ground&quot;.  You could also use V+ as your &quot;ground&quot; to get a -48 V supply.
This type of supply is &quot;isolated&quot; meaning there is not normally a connection between V- and Earth.  You can connect them together, if you need your DC ground to be common with Earth.
The decision comes down to whether or not you want your DC ground to be tied to Earth potential.