Yesterday, I wanted to test some MCBs and power supplies that I had just received. Since we only have one 480V socket in the shop, I asked my coworker if I could use the power source he was using. He went with me and unplugged his (working) PLC system which used a 3 pole MCB powering a 24VDC power supply. His parts are nearly identical to the parts I'm testing.
I took an identical power cable we had and wired in three of the wires to one of my MCBs. I left the remaining green wire that had a ring terminal on it unconnected.
When I plugged in the cable and measured the voltages at the MCB, I was confused at the measurements. If we call the three phase wires A, B, and C, and the green wire D, then these were the measurements I made:
We're in western Canada, and I've heard that some systems use a "high leg", but I don't think that's what we have here. I also read about "corner grounded" and "open" delta systems, but I don't know if that's what we have.
What kind of distribution system is this?
Given that my coworker's system hasn't malfunctioned, it may be safe to say that I can simply treat it as a 480V three-phase connection and not worry about how it works. Is this stupid?