From: Richard W. Schauer <rws(a)enteract.com> got would 208v is Rewire. The reason most of these devices use three phase is to distribute a load more uniformly over what was a normal power system in computer rooms then. Also many of these devices have a rather harsh startup current and slicing it two or three ways makes it much easier for the sytem (wiring and power circuits) to sustain. For example a lowly MVII in a BA23 has a startup surge of over 100A for one cycle (about 16mS). In the second 16mS that might be only 12A and by the 10th your near nominal of say 3.2A. If you turned ten of them on at the same time and same circuit the running current is maybe 32-40A but the starting current could easily exceed 1000A for several cycles. Why? If they were all on one breaker the whole load would attempt to bring the caps in the power supply up that first 16mS... save for the 10,000A surge would pull the 115v down to say 60V (assuming thick wires and the fuses held!) the next cycle would be needed to charge those caps more, likely 10 or 15 cycles so the huge current would take longer to dissapate. Add motors like the RP06 with their nasty starting currents and you see why power systems were so robust. Granted the startup condition is pathological as no one would do that (staggered is also common) but the need to distribute the sustained load is also important. If I had a 6000, I'd ahve rewired it already and could tell. Most often (but not always) three phase power is used as independant legs. Exceptions would be beasties like VAX9000, PDP10s and other power hungry older machines. Allison