PV system Point of Interconnection and Voltage Range

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inforaj

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For Commercial purposes, We have a small customer that needs to install three separate solar systems (each 5KW DC) for 3-customers, and the Point of Interconnection grid had available 3-phase voltage (277/480V AC). and I found the Inverter SMA that had a nominal voltage range is 3/N/PE; 220V/380V, 3/N/PE; 230V/400 V, and 3/N/PE; 240V/415 V.
I am wondering if there is an issue with the Point of interconnections. Does this work for Point of Interconnection or Not? If yes, is there any issue for Inverter to get trip (turn off and turn on due to the voltage range)
Appreciate your help.
 
Those inverters will not work on a 480/277V system. I am not aware of any 3ph 5kW inverters, I don't know of any 3ph inverters less than 30kW or so. What you are probably going to have to do is use a 480:120/240V transformer to give you 240V single-phase and use a single-phase inverter.
 
inforaj said:
For Commercial purposes, We have a small customer that needs to install three separate solar systems (each 5KW DC) for 3-customers, and the Point of Interconnection grid had available 3-phase voltage (277/480V AC). and I found the Inverter SMA that had a nominal voltage range is 3/N/PE; 220V/380V, 3/N/PE; 230V/400 V, and 3/N/PE; 240V/415 V.
I am wondering if there is an issue with the Point of interconnections. Does this work for Point of Interconnection or Not? If yes, is there any issue for Inverter to get trip (turn off and turn on due to the voltage range)
Appreciate your help.
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The customers likely have transformers to step down the 480/277V supply to 240V or 208/120V; can you interconnect on their secondary side?
 
pv_n00b said:
Those inverters will not work on a 480/277V system. I am not aware of any 3ph 5kW inverters, I don't know of any 3ph inverters less than 30kW or so. What you are probably going to have to do is use a 480:120/240V transformer to give you 240V single-phase and use a single-phase inverter.
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The main panel is 277/480 volts, and all machines are connected in 277/480 v panels. One small panel with a 3-phase to single-phase transformer is also available for lighting and receptacles purposes.
 
ggunn said:
The customers likely have transformers to step down the 480/277V supply to 240V or 208/120V; can you interconnect on their secondary side?
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The 208/120V is only for lighting and Receptacles use, but many machines and equipment are connected in 480/277V panels.
 
inforaj said:
The 208/120V is only for lighting and Receptacles use, but many machines and equipment are connected in 480/277V panels.
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If the transformers powering the 208/120V loads are large enough (kVA of transformer = or > kW of inverter) to accommodate them, wouldn't you be able to interconnect on their secondary side? The PV systems you mention are so small that it seems that they might fit. Otherwise you'll have to install your own transformers; no one makes 480/277V inverters that small.
 
inforaj said:
I found the Inverter SMA that had a nominal voltage range is 3/N/PE; 220V/380V, 3/N/PE; 230V/400 V, and 3/N/PE; 240V/415 V.
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It sounds like you are looking at a datasheet for the rest of the world from SMA Germany, rather than for North America. Perhaps you are looking at sma.de/en/, rather than sma-america.com.

The smallest 3-phase inverter that I know about for the 277/480V grid, is SolarEdge's 10kW inverter. You are probably better off finding a way to connect to the customers' 120/208V sides of their smaller transformers, since you can find single phase inverters that can work at either 208V or 240V instead. Most buildings at 277/480V will still require a portion of their distribution system to be at 120V in some form or another, in order to power the general purpose receptacles and the minority of the loads that can't use the main service voltage directly. It is most common for it to be derived via a 3-phase transformer that the customer owns, with a 120/208V wye secondary.

Keep in mind that you may have a reduction in the inverter power rating when connecting a 240V inverter to the 208V grid. For instance, a 6 kW inverter may become 5 kW, because that is what is necessary in order to satisfy P=I*V when I is fixed, and V decreases to 86%. When inverters had integrated transformers, it was a matter of changing the taps on the AC output and current would increase to compensate. But with transformerless inverters, it is a firmware adjustment to adapt to the slightly lower voltage, and the current is stuck at the value that was set with a 240V grid in mind.

There used to be single phase inverters that could connect to 277V single phase breakers on a 277/480V grid. The transformer tap selector would allow selecting either 208V, 240V, or 277V. This is no longer the way most single phase inverters are built.
 
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Carultch said:
There used to be single phase inverters that could connect to 277V single phase breakers on a 277/480V grid. The transformer tap selector would allow selecting either 208V, 240V, or 277V. This is no longer the way most single phase inverters are built.
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Uninformed question: are there transformerless single phase inverters currently available that will work on a 240V corner grounded delta, and if so, could one couple such an inverter with a buck transformer from 277V to 240V? Or would it need to be a 277V - 240V isolation transformer?

Cheers, Wayne
 
wwhitney said:
Uninformed question: are there transformerless single phase inverters currently available that will work on a 240V corner grounded delta, and if so, could one couple such an inverter with a buck transformer from 277V to 240V? Or would it need to be a 277V - 240V isolation transformer?

Cheers, Wayne
Click to expand...

Yes, there are transformerless single phase inverters that can work on corner-grounded 240V delta grids, or even using the B-phase of high leg delta grids. I have not explored your proposed solution completely to rule out all potential issues, but it would logically would follow that a 277V:240V autotransformer could generate a 240V end-grounded grid that would seemingly be no different to the inverter than if it were connected to a corner-grounded phase and an ungrounded phase. You'd need to check product specifics to see what they require of the neutral (if anything), and what voltage-to-ground is required for L1 and L2. Some inverters may have an internal power supply that uses the neutral, and therefore couldn't work with L1 grounded and L2 at 240V.

From what I see in the manual of the currently-available SMA Sunny Boy inverters, they can work with either 208V or 240V between L1 and L2, and L1 and L2 can be up to 240V to ground. You lose your secure power supply when you don't have 120V-to-neutral on L1 and L2, but that's the only downside I'm seeing in its manual.
 
wwhitney said:
Uninformed question: are there transformerless single phase inverters currently available that will work on a 240V corner grounded delta, and if so, could one couple such an inverter with a buck transformer from 277V to 240V? Or would it need to be a 277V - 240V isolation transformer?

Cheers, Wayne
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Since the voltage to ground in a corner grounded delta is going to be 240V that might mess with a single-phase inverter even if not connected to the grounded phase. I've not looked into doing this since corner grounded delta services are very rare now in CA. Where are these corner grounded delta services still being used?
 
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