<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;">Measuring current without the phase relationship between the current and voltage<br>isn't indicative of the actual power consumed. Likely what you were seeing is the<br>eddy current in the transformer core. If so, it's 90 degrees out of phase with the<br>voltage, and the real wattage consumed with no load connected is minimal.<br><br>Dan<br>Sr. Engineer<br>Exeltech<br><br><br>--- On <b>Mon, 7/25/11, Mark Frye <i><markf@berkeleysolar.com></i></b> wrote:<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;"><br>From: Mark Frye <markf@berkeleysolar.com><br>Subject: Re: [RE-wrenches] Efficient step up, down transformers<br>To: "'RE-wrenches'" <re-wrenches@lists.re-wrenches.org><br>Date: Monday, July 25, 2011, 10:11 AM<br><br><div id="yiv1278360479">
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<div dir="ltr" align="left"><font color="#0000ff" face="Arial" size="2"><span class="yiv1278360479500105014-25072011">Lars,</span></font></div>
<div dir="ltr" align="left"><font color="#0000ff" face="Arial" size="2"><span class="yiv1278360479500105014-25072011"></span></font> </div>
<div dir="ltr" align="left"><font color="#0000ff" face="Arial" size="2"><span class="yiv1278360479500105014-25072011">Scary stuff. I worked with a system similar to this and
went with big wire.</span></font></div>
<div dir="ltr" align="left"><font color="#0000ff" face="Arial" size="2"><span class="yiv1278360479500105014-25072011"></span></font> </div>
<div dir="ltr" align="left"><font color="#0000ff" face="Arial" size="2"><span class="yiv1278360479500105014-25072011">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. </span></font></div>
<div dir="ltr" align="left"><font color="#0000ff" face="Arial" size="2"><span class="yiv1278360479500105014-25072011"></span></font> </div>
<div dir="ltr" align="left"><font color="#0000ff" face="Arial" size="2"><span class="yiv1278360479500105014-25072011">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.</span></font></div>
<div><font color="#0000ff" face="Arial" size="2"></font> </div>
<div><span class="yiv1278360479500105014-25072011"><font color="#0000ff" face="Arial" size="2">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.</font></span></div>
<div><span class="yiv1278360479500105014-25072011"><font color="#0000ff" face="Arial" size="2"></font></span><span class="yiv1278360479500105014-25072011"><font color="#0000ff" face="Arial" size="2"></font></span> </div>
<div><font color="#0000ff" face="Arial" size="2"><span class="yiv1278360479500105014-25072011">I
would be happy to stop by and take a look at the xfrm spec etc. with
you.</span></font></div>
<div><br><span lang="en-us"><font face="Arial" size="2">Mark Frye</font></span>
<br><span lang="en-us"><font face="Arial" size="2">Berkeley Solar Electric
Systems</font></span> <br><span lang="en-us"><font face="Arial" size="2">303 Redbud
Way</font></span> <br><span lang="en-us"><font face="Arial" size="2">Nevada
City, CA 95959</font></span> <br><span lang="en-us"><font face="Arial" size="2">(530) 401-8024</font></span> <br><span lang="en-us"></span><a rel="nofollow" target="_blank" href="http://www.berkeleysolar.com/"><span lang="en-us"><u><font color="#0000ff" face="Arial" size="2">www.berkeleysolar.com</font></u></span></a><span lang="en-us"><font face="Arial" size="2"> </font></span> </div>
<div> </div><br>
<div dir="ltr" class="yiv1278360479OutlookMessageHeader" align="left" lang="en-us">
<hr tabindex="-1">
<font face="Tahoma" size="2"><b>From:</b> re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <b>On Behalf Of </b>lars
Ortegren<br><b>Sent:</b> Monday, July 25, 2011 7:43 AM<br><b>To:</b>
re-wrenches@lists.re-wrenches.org<br><b>Subject:</b> [RE-wrenches] Efficient
step up, down transformers<br></font><br></div>
<div></div>
<div class="yiv1278360479WordSection1">
<p class="yiv1278360479MsoNormal">Wrenches,</p>
<p class="yiv1278360479MsoNormal">
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!</p>
<p class="yiv1278360479MsoNormal"> </p>
<p class="yiv1278360479MsoNormal"><b><i>Lars Ortegren</i></b></p>
<p class="yiv1278360479MsoNormal"> </p>
<p class="yiv1278360479MsoNormal"><span style="font-family: 'serif';">Director of
Operations</span></p>
<p class="yiv1278360479MsoNormal"><span style="font-family: 'sans-serif'; color: rgb(0, 32, 96); font-size: 12pt;">California
Solar Electric Company</span></p>
<p class="yiv1278360479MsoNormal">10141 Evening Star Drive, Suite 6</p>
<p class="yiv1278360479MsoNormal">Grass Valley, CA 95945</p>
<p class="yiv1278360479MsoNormal"> </p>
<p class="yiv1278360479MsoNormal">Phone : (530)274-3671</p>
<p class="yiv1278360479MsoNormal">Fax: (530)274-7518</p>
<p class="yiv1278360479MsoNormal"> <br></p></div></div></blockquote></td></tr></table>