Dan:
We are not desiring 120 degrees. We are desiring 180 degrees, and it can
be derived, and without a Scott-T. I have done this recently.
William Miller
At 08:26 PM 10/23/2011, you wrote:
Mac,
You can't get a 120 degree phase shift from a transformer with windings on
a common core. Two transformers can be combined in a "Scott-T"
configuration" to synthesize a 120 degree shift, but special transformers
are required. Also, a Scott-T configuration must be used with closely
balanced loads between phases.
There's an explanation of how a Scott-T topology works at this link:
http://en.wikipedia.org/wiki/Scott-T_transformer
Dan
--- On Sun, 10/23/11, mac Lewis <maclew...@gmail.com> wrote:
From: mac Lewis <maclew...@gmail.com>
Subject: Re: [RE-wrenches] Three-phase off-grid
To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org>
Date: Sunday, October 23, 2011, 9:02 PM
Wrenches,
Is it a "special" transformer that will give you the 180 deg phase shift
from the original 120 deg shift?
Thanks
On Fri, Oct 21, 2011 at 5:52 PM, William Miller <will...@millersolar.com>
wrote:
Friends:
I posted a question here about three weeks ago on the subject of
connecting a dual SW inverter stack to a three phase generator. I have
learned a lot since then. Here are the most important points:
Most large, three phase generators are allegedly field convertible to be
either 208 or 240 three phase. The 208 version is probably wye
configured and the phase angle between any two phases is 120 degrees. If
you connect a 120/240 inverter system (even numbers of Outbacks, two SW's
or XWs configured single phase, and maybe other models) across two of the
phases, the 120 degree phasing will cause the inverters to puke. If you
purchase and connect the correct transformer across two of these phases
and you will provide the 180 degree phase angle you need but you will
imbalance the generator. For a large (30KVA or larger) generator, the 10
KVA of imbalance is not a big issue. Your transformer will cost about
$1,000 delivered and will weigh about 200 pounds.
You can swap some connectors and have a 240 configuration which will
probably have a "stinger" leg. If it does, the windings are probably a
delta with one winding center tapped. If so, the phase angle between the
two phases on either side of the neutral is 180 degrees. You can connect
your Outbacks (or others) across these two phases and neutral without a
transformer. You'e saved your client $1,000 and yourself a hernia.
If the customer can live with a stinger then you have your cake and eat
it too: Three phase for 240 VAC loads and a 120/240 single phase
inverter system for 120 or 240 VAC loads.
This realization was huge to me. Think about it...
William Miller
PS: Just replacing a 3 phase panel with a single phase panel does not
give you 120/240 with 180 degree phase angle.
Wm
At 08:23 AM 10/21/2011, you wrote:
Do they actually have 208v loads? If not, replace with 120/240 panel.
Just a thought... Although a transformer would be required to use an
existing 208v generator.
Jason Szumlanski
On Oct 21, 2011, at 11:17 AM, "Allan Sindelar"
<al...@positiveenergysolar.com> wrote:
Wrenches,
We have been asked for a design for an off-grid system to reduce
generator runtime for a mountain resort. Initial projections
(consumption measurement results not yet available) suggest 15-20 kW of
PV and around 30 kW of inverter capacity. However, the generators and
existing wiring are three-phase 120/208.
My assumption is that our only options are a set of six Sunny Islands,
or 9-12 Outback GVFX3648s. Are there any other options or approaches
that I'm missing?
Thank you, Allan
--
A
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches@lists.re-wrenches.org
Options & settings:
<http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org>http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive:
<http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org>http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
<http://www.re-wrenches.org/etiquette.htm>www.re-wrenches.org/etiquette.htm
Check out participant bios:
<http://www.members.re-wrenches.org>www.members.re-wrenches.org
--
Mac Lewis
"Yo solo sé que no sé nada." -Sócrates
-----Inline Attachment Follows-----
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches@lists.re-wrenches.org
Options & settings:
<http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org>http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive:
<http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org>http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches@lists.re-wrenches.org
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive:
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
No virus found in this incoming message.
Checked by AVG - www.avg.com
Version: 8.5.454 / Virus Database: 271.1.1/3970 - Release Date: 10/23/11
18:33:00
Miller Solar
Voice :805-438-5600
email: will...@millersolar.com
http://millersolar.com
License No. C-10-773985
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches@lists.re-wrenches.org
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
