----- Original Message -----
From: "Michael Loftis" <mloftis@wgops.com>
On Fri, Dec 3, 2010 at 10:33 PM, Jay Ashworth <jra@baylink.com> wrote:
And in fact, much carrier class equipment can be had with -48V power, there are ATX and similar power supplies for PCs that are -48, and I *think* I've seen commercial small UPSs (<3kVa) that give with -48 as well... using 48V battery strings, obviously.
Take a look at the Solar/Renewable energy systems, Xantrex (Schneider actually) makes the XW series inverter/chargers which use 48V battery strings and can be paralleled up to a rated total of about 18kW@120/240. This is done by paralleling 3x 6kW inverter/chargers. They've an integrated transfer switch, load shaving/sharing (IE if you've got say 6kW of generator, but 12kW of Inverter, the system capacity is up to 12kW, with battery assist).
And that's just one option, Magnasine makes parallel inverter/charger and inverter systems up to around 12kW, also using 48VDC (or 24VDC) strings.
Both of these are sinewave inverters.
There's also a telco oriented 48V inverter rack system thats escaping my mind at the moment. It can be setup with A/B 48V strings, and you plug in inverter modules up to IIRC around 8kW. Not parallel capable between racks AFAIK.
I phrased my comment poorly, which mislead you. I was suggesting a UPS which took 208VAC on on the charge side, and charged 48VDC batteries with it, providing -48 to a rack full of equipment which took that. People actually call those "48VDC UPSs", though in fact they're just Little Teeny Battery Plants. :-) Cheers, -- jra