I based my wiring plan on @kd2018’s excellent wiring schematic for his LR2 based plasma cutter, shared here on V1E forum. It calls for use of “star ground” for the power supplies etc.
I’m using a metal case (formerly a PC desktop tower, revamped for this need). It had the case grounded to the main power at the point of entry. I disconnected that to use the “star ground” approach, but my question is, shouldn’t the case be grounded too?
As I see it, the options are below, and for plasma cutting, there are all these concerns about electromagnetic noise and interference and one has to be careful about grounding and how it is done.
Option 1: use “star ground” and not ground the case.
Option 2: use “star ground” and also ground the case.
Option 3: do not use “star ground” and instead ground the case, and connect the items to the case for grounding them.
For audio circuits the concept of a star ground is to eliminate ground loops, because loops act as antenna ti pick up noise.
Ultimately, ground should connect to earth. The earth ground coming in with the AC power is a good place to do it. DC circuits, like car audio will ground to the car chassis, which doubles as DC Negative.
My audio circuits will have the star ground usually on a chunk of cooper, near the power entry, and usually the power transformer, or SMPS in the cases where I use it. The chassis is nearly always grounded as well. This does not negate the star ground, but enhances it. If the enclosure chassis is a good enough conductor, the star ground point can be a stud bonded to it. This works well for a pre-amplifier system and helps with noise rejection.
