[RE-wrenches] Efficient step up, down transformers

[Jason Szumlanski]

The wire would be a one-time-cost. Even "ultra-efficient" transformers
cheat you out of energy for the long-haul, and are an added potential
point of failure.

 

We are running into customers that have 480V service with 480->120/208
transformers and they want Enphase microinverters. I cringe a little,
but go with it if the sustained loads on the secondary side of the
transformer are likely to consume all of the PV production. On a larger
system (relative to consumption) I would insist on a 480V inverter.

 

Jason Szumlanski

Fafco Solar 

 

 

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 11:11 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 <http://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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