[RE-wrenches] Efficient step up, down transformers

[Exeltech]

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 <dana at solarwork.com> wrote:

From: Dana <dana at solarwork.com>
Subject: Re: [RE-wrenches] Efficient step up, down transformers
To: "'RE-wrenches'" <re-wrenches at 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 - dana at 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-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at 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-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of lars Ortegren
Sent: Monday, July 25, 2011 7:43 AM
To: re-wrenches at 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  
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