Hello William, It works as long as you tie into just one phase of the three-phase system for the input .. from which you can then derive single-phase output. A 180 degree shift is also do-able with multiple output windings in the transformer.
Still recovering from SPI. It was a *long* week. Dan --- On Sun, 10/23/11, William Miller <[email protected]> wrote: From: William Miller <[email protected]> Subject: Re: [RE-wrenches] Three-phase off-grid To: "RE-wrenches" <[email protected]> Date: Sunday, October 23, 2011, 11:30 PM 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 <[email protected]> wrote: From: mac Lewis <[email protected]> Subject: Re: [RE-wrenches] Three-phase off-grid To: "RE-wrenches" <[email protected]> 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 <[email protected]> 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" <[email protected]> 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: [email protected] 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 -- Mac Lewis "Yo solo sé que no sé nada." -Sócrates -----Inline Attachment Follows----- _______________________________________________ List sponsored by Home Power magazine List Address: [email protected] 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_______________________________________________ List sponsored by Home Power magazine List Address: [email protected] 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. 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