Ok, I think by balanced or unbalanced they mean the amount of current draw on an electrical panel or supply. If you have a single phase, by definition it is unbalanced since there is nothing to balance. However, with more than one phase, you can try to draw similarly between them.
The z10-BC Physical Planning manual (GC28-6875-03) has a section on 'Balancing power panel loads'. In there it says: "For z10 BC models that use three phase power, depending on the system configuration, the phase currents can be fully balanced or unbalanced. For each possible drawer configuration (processor and I/O combinations), any given system presents a balanced or unbalanced load. If several unbalanced system configurations are fed from the same power panel, the load on that panel will be unbalanced. Two phase currents will be equal and both will be, nominally, 57.8% of the current on the third phase." I think it's clear now. Aria From: The IBM z/VM Operating System [mailto:ib...@listserv.uark.edu] On Behalf Of P S Sent: Tuesday, December 22, 2009 10:19 AM To: IBMVM@LISTSERV.UARK.EDU Subject: Re: z890 power: 3 phase vs 1 phase? On Tue, Dec 22, 2009 at 10:14 AM, Aria Bamdad <a...@bsc.gwu.edu> wrote: I am not totally clear as to what balanced and unbalanced power means. I plan to find out tomorrow when I speak to my CE. Looking online and doing a search for "balanced power systems" makes me think that it has something to do with the current draw on each phase. Being single phase, I can understand why it cannot be balanced. If I find the true answer, I will post here. The more important thing is that it seems that with single phase power, you cannot have beyond a specific amount of I/O drawers. Indeed, I did notice that! Thanks, will be interesting to hear. With only one phase, wouldn't it be balanced by definition -- how can you draw differently on other phases that don't exist? :-)
