ECN Electrical Forum
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IBM had so much trouble getting the phasing right in computer rooms the machines started coming with phase rotation detection and a reversing plug right in the power supply. Red light on and no power, pull the reversing plug out, flip it over and plug it in.
Prior to that somebody was moving a couple wires.

Since when do computer power supplies care about phasing? Typically when I see machines big enough to require "three phase power", all that means is they send each phase to a separate power supply module which connects between it and ground.

Maybe the stuff you describe was more exotic.

I found the same with our old 3-phase computers, just sending each phase to a separate power supply module. I have not looked that close at our newest IBM stuff, but I suspect the same at worst.

We had lots of 3 phase motors in the old stuff. (before everything was basically a PC). Even the gate blowers were 3 phase. It helped balance the load. Some power supplies were 3 phase, some just tapped off 2 phases and were basically single phase. Those there the ones you had to be careful with on red leg delta.