Expensive mistake

Post #14,689 by broomberg 10/22/01 9:26:26 PM Reply	Expensive mistake Oh, to have all this electrical knowledge. As opposed to me, who screwed up and ordered a pure 220V UPS, and am unable to return it. Really. I've got a computer room filled with both 110 and 220 gear. But since I typically deal with 2TB, 4 Sun 450s, and 6 Linux boxes at a time (including power), I will get several UPSs for each project. I like APC MX5000 Extended Run, which I typically get via CDW: [link\|http://www.cdw.com/shop/products/default.asp?EDC=079017\|http://www.cdw.com/...p?EDC=079017] But there is a model listed MX5000, exactly the same (or so I thought), but is the pure European model, which means these wierd 220V plugs (but only a piddly max 15AMP per plug, I use 30 amp 220V for my big boxen). CDW told me to jam it, they weren't taking it back. So I've blown about $7000 on 2 of them. I'l scavenge the battery portion and daisy chain them off another one, but the main unit is a waste. Oh well.
Post #14,731 by Ashton 10/23/01 3:43:25 AM Reply	Well.. one possibility If it's the ~pure sinewave version: 2:1 step-down transformer - though it will be a bit hefty at 3 KW/plug. This won't work for the modified-square-wave of the usual output, intended for switching PS's. (Dunno if Sun uses linear PSs, for some of their ovens?) (I can't quite see why they'd be unwilling to take it back unused, though. Especially ordering in that league) Let me know if you plan to toss the guts, please - though I haven't any immediate ideas for use of such a gadget.. Ashton
Post #14,880 by Ric Locke 10/23/01 11:47:50 PM Reply	220 UPS outputs Check the PSs on your boxen. Many, many of the better quality power supplies nowadays are "universal input", allowing 85 - 245 or 95 - 265V inputs; just change the power cord w/IEC connector for the plug in country of choice. Cuts down on the inventory problems... I'd imagine anything as expensive as a Sun would have such a supply; huge numbers of relatively cheap PCs do. Even in cases of non-universal input, many still have the switch to allow hi/lo AC input [though it isn't the old-fashioned transformer windings; dunno exactly how they do it -- switching power supplies are black magic to me] And re: 110/220 -- the one that bugs me is three-phase. First off, why isn't three-phase more common? Wonderful power saver for motors; you could probably make a sizeable dent in base power consumption just by running refrigerators on three-phase power instead of using shaded-pole motors, and my God the air conditioners. Here in the US we use "Delta" -- the three phases are arranged in a triangle. When it comes onto a premises, there's a ground in the middle of one side. Each side is thus 220 with respect to any other point, but reading from ground, you've got 110, 100, and the "wild phase", 208 volts. Trouble with that is circulating current; if the transformers don't exactly match, current flows around the loop, accomplishing nothing but heating the air. Other countries use "star" (also called "wye"), in which ground is the center and the three windings branch off, not interconnected. No circulating current, better efficiency. 110V three-phase wye would yield about 190V phase-to-phase, and running all three phases would (if the equipment were available) improve efficiency. Is it all a case of coping with legacy (=antique) gear? Regards, Ric

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