Measuring current without the phase relationship between the current and voltage
isn't indicative of the actual power consumed. Likely what you were seeing is
the
eddy current in the transformer core. If so, it's 90 degrees out of phase with
the
voltage, and the real wattage consumed with no load connected is minimal.
Dan
Sr. Engineer
Exeltech
--- On Mon, 7/25/11, Mark Frye <ma...@berkeleysolar.com> wrote:
From: Mark Frye <ma...@berkeleysolar.com>
Subject: Re: [RE-wrenches] Efficient step up, down transformers
To: "'RE-wrenches'" <re-wrenches@lists.re-wrenches.org>
Date: Monday, July 25, 2011, 10:11 AM
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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 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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