[RE-wrenches] Efficient step up, down transformers

[Exeltech]

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 <markf at berkeleysolar.com> wrote:

From: Mark Frye <markf at berkeleysolar.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, 10:11 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-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 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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