It's possible, depending on the transformer construction. We've evaluated transformers that are spec'd up to 99% efficient, but these were special transformers.
I don't know what type of transformer Lars was considering. Dan --- On Mon, 7/25/11, Dana <d...@solarwork.com> wrote: From: Dana <d...@solarwork.com> Subject: Re: [RE-wrenches] Efficient step up, down transformers To: "'RE-wrenches'" <re-wrenches@lists.re-wrenches.org> Date: Monday, July 25, 2011, 10:16 AM Seriously I have never heard of 99% eff. under load with a transformer. Anyone else heard of this kind of eff. factor? Dana OrzelGreat Solar Works, IncE - d...@solarwork.comv - 970.626.5253F - 970.626.4140C - 970.209.4076web - www.solarwork.com "Responsible Technologies for Responsible People since 1988"Do not ever believe anything, but seriously trust through action. From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Mark Frye Sent: Monday, July 25, 2011 9:11 AM To: 'RE-wrenches' Subject: Re: [RE-wrenches] Efficient step up, down transformers 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 www.berkeleysolar.com From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of lars Ortegren Sent: Monday, July 25, 2011 7:43 AM To: re-wrenches@lists.re-wrenches.org Subject: [RE-wrenches] Efficient step up, down transformersWrenches, 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 OperationsCalifornia Solar Electric Company10141 Evening Star Drive, Suite 6Grass Valley, CA 95945 Phone : (530)274-3671Fax: (530)274-7518 -----Inline Attachment Follows----- _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
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