Lars, Scary stuff. I worked with a system similar to this and went with big wire. The problem with xfrms is that you can either have low standby losses and good efficency at load or vis-a-versa, but you can't really have both. Were the xfrms specifically wound for 120x480 conversion? If not, it is possible that the coil taps are connected in a manner that is not efficient. That being said, 15.6 A @ 120V sound like an awefully large number. Perhaps you have a bad connection at one of your pull boxes. I would be happy to stop by and take a look at the xfrm spec etc. with you.
Mark Frye Berkeley Solar Electric Systems 303 Redbud Way Nevada City, CA 95959 (530) 401-8024 <http://www.berkeleysolar.com/> www.berkeleysolar.com _____ From: [email protected] [mailto:[email protected]] On Behalf Of lars Ortegren Sent: Monday, July 25, 2011 7:43 AM To: [email protected] Subject: [RE-wrenches] Efficient step up, down transformers Wrenches, I recently installed three "ultra -efficient" step up-down transformers on an off grid micro grid project with a 1500' wire run. The grid is powered by a an old SW4024(120v) output, stepped up to 480v, and stepped down to 240v at two locations. I was told by the manufacturer that they were "99% efficient under a full load", but upon firing up the system, I found a NO LOAD AMPEREAGE OF 15.6 amps!!! Needless to say, a completely unworkable situation for an off grid scenario, as the 840ah battery would be drained in a couple of hours before anything was turned on. I'm wondering if anyone out there has either found off grid friendly step up-down transformers, or if I'm just screwed and need to pull parallel 4/0 runs (probably the price of a new car) to fix the problem. HELP! Lars Ortegren Director of Operations California Solar Electric Company 10141 Evening Star Drive, Suite 6 Grass Valley, CA 95945 Phone : (530)274-3671 Fax: (530)274-7518
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