Photovoltaic; Single-Phase Inverter on Three-Phase System
Photovoltaic; Single-Phase Inverter on Three-Phase System
(OP)
Multi-tenant (nine meters) warehouse, fed 240V-delta. Three customers use the 240V three-phase service, remaining customers use the 120/240V single-phase service. Three single-phase customers plan to install PV using 240V single-phase inverters.
Installation is allowed per NEC 690.63(A); however, the wording "shall not be connected to 3-phase power systems unless the interconnected system is designed so that significant unbalanced voltages cannot result" is a tough one as this is a 1980s-era building that has experienced multiple interior alterations (new install could at least have a good shot at balancing the loads, including tenants not benefiting from the PV).
Will connect the inverter outputs across the center-tapped phases, but would appreciate any input on the best way to approach the (possible) unbalanced issue.
Installation is allowed per NEC 690.63(A); however, the wording "shall not be connected to 3-phase power systems unless the interconnected system is designed so that significant unbalanced voltages cannot result" is a tough one as this is a 1980s-era building that has experienced multiple interior alterations (new install could at least have a good shot at balancing the loads, including tenants not benefiting from the PV).
Will connect the inverter outputs across the center-tapped phases, but would appreciate any input on the best way to approach the (possible) unbalanced issue.






RE: Photovoltaic; Single-Phase Inverter on Three-Phase System
RE: Photovoltaic; Single-Phase Inverter on Three-Phase System
Alan
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"It's always fun to do the impossible." - Walt Disney
RE: Photovoltaic; Single-Phase Inverter on Three-Phase System
Three single phase customers on a four wire delta system will probably cause slight voltage unbalances as will 120V loads and some 240 volt single phase loads on the three phase services.
I don't see a serious voltage balance issue with a reasonable amount of PV input.Most of the time it will act to partially correct the voltage unbalances inherent in the basic connection.
The Authority Having Jurisdiction and the power utility will have to approve the installation.
Bill
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"Why not the best?"
Jimmy Carter
RE: Photovoltaic; Single-Phase Inverter on Three-Phase System
Agree with Ahleman - it would be best to connect the inverter outputs to the non-wild legs. But that probably complicates the installation quite a bit.
Might be a good time to think about cleaning this service up. Separate out the few needing three-phase and put in new transformers to serve the single-phase customers.
"An 'expert' is someone who has made every possible mistake in a very narrow field of study." -- Edward Teller
RE: Photovoltaic; Single-Phase Inverter on Three-Phase System
RE: Photovoltaic; Single-Phase Inverter on Three-Phase System
Alan
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"It's always fun to do the impossible." - Walt Disney