Garrison:
Are you sure you need a transformer to connect directly to the 3 phase? I believe the system you refer to is an open-delta. We've installed the old SB2500 units on open-delta before. This was before the neutral sensing requirements, however. Many inverters have provisions for disabling the neutral sense, if that would help. I'd verify there is actually a need for a transformer. William PS: I do remember that I incorrectly ordered 208 inverters for the open-delta installation referred to above. It was actually a 240 volt three phase. The SB2500s had to be specified for the correct voltage. I had to eat a lot of freight to get 5 inverters reconfigured.. Wm Gradient Cap_mini Lic 773985 <http://www.millersolar.com/> millersolar.com 805-438-5600 From: RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Garrison Riegel Sent: Friday, November 14, 2014 7:51 AM To: re-wrenches@lists.re-wrenches.org Subject: [RE-wrenches] Preventing 24/7 Transformer Losses Hello Wrenches, In my area we end up installing a lot of systems on 240V 3Ph high leg services. To allow for more inverter options (like TL that require a neutral) it seems like using a transformer would a good idea, but it is hard to justify the losses under load and especially 24/7 losses required to keep the core magnetized. In a recent post on this same subject by Greg Smith from SMA he wrote, "If you specify a transformer specifically for solar PV designs then the losses are negligible." The transformer tech people at the manufacturers I spoken with have no idea what this means. I emailed Greg for clarification but have not yet had a reply. On a recent project that needed a 30KVA transformer the 24/7 losses were 200-300W depending on manufacturer, which is not negligible, and in my area would require about 2kW of PV to offset. Does anyone know what Greg might be referring to? What are folks doing to mitigate these losses? Some kind of DC actuated switch on the utility side of the transformer maybe? Anything else to keep in mind when specifying a PV specific transformer? Thank you for your thoughts. Garrison Garrison Riegel Project Manager | <http://www.solarserviceinc.com/> Solar Service Inc [p] 847-677-0950 | <mailto:garri...@solarserviceinc.com> garri...@solarserviceinc.com NABCEP Certified PV Installation ProfessionalT
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