three phase inverter connection for 240/208/120 v 3 PHASE 4 WIRE DELTA

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Designer101

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Solar and ESS Designer
I designed the 33 kw commercial system with two 14.4k us soalredge 3 phase inverter systems, guys at installation site says they measure 120/120/280 L-N, what can be done to make this 120/120/120 through each line- neutral??
or how to fix this? is there any way we use 3 single SolarEdge phase inverter and what will happen to neutral of each inverter? the problem is I have only 100A of backfeed available?
Please suggest
 

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They might want to put new batteries in their meter, delta services do not put out 280 to Neutral! LOL! Don’t know much about solar, but to get 120 to neutral across the board, the service would need to be changed from a delta to a wye.
 
I think he meant 208 according to the title.
You have a high leg delta it sounds like.
 
Designer101 said:
I designed the 33 kw commercial system with two 14.4k us soalredge 3 phase inverter systems, guys at installation site says they measure 120/120/280 L-N, what can be done to make this 120/120/120 through each line- neutral??
or how to fix this? is there any way we use 3 single SolarEdge phase inverter and what will happen to neutral of each inverter? the problem is I have only 100A of backfeed available?
Please suggest
Click to expand...
Designer101 said:
I designed the 33 kw commercial system with two 14.4k us soalredge 3 phase inverter systems, guys at installation site says they measure 120/120/280 L-N, what can be done to make this 120/120/120 through each line- neutral??
or how to fix this? is there any way we use 3 single SolarEdge phase inverter and what will happen to neutral of each inverter? the problem is I have only 100A of backfeed available?
Please suggest
Click to expand...
hillbilly1 said:
They might want to put new batteries in their meter, delta services do not put out 280 to Neutral! LOL! Don’t know much about solar, but to get 120 to neutral across the board, the service would need to be changed from a delta to a wye.
Click to expand...
my bad it should be 208
 
A 240V delta to 208V wye transformer such as this one would help:

store.maddoxtransformer.com

3-Phase 240V Delta - 208 Y 120

This transformer is designed to convert 3-phase 240v to 3-phase 208 Y 120 to run equipment such as panels, motors, CNC machines, welders, conveyor systems, pumps, printing equipment, fabrication tools, and other business machines. Primary Voltage: 240 Delta Secondary Voltage: 208 Y 120...
store.maddoxtransformer.com store.maddoxtransformer.com
 
I have zero experience in this, just questions. Does each inverter put out 3-phase, or do you have 2 single phase inverters tied together (like transformers) to put out a Delta 4-wire (is that even possible)? If they both put out 3-phase, are they paralleled?
 
oldsparky52 said:
I have zero experience in this, just questions. Does each inverter put out 3-phase, or do you have 2 single phase inverters tied together (like transformers) to put out a Delta 4-wire (is that even possible)? If they both put out 3-phase, are they paralleled?
Click to expand...

This family of inverters, requires 208V phase-to-phase, and can either connect to 208V delta or 120/208 wye. Its 277/480V counterparts require a neutral and a 277/480V wye grid.

Either the datasheet or manual will spell out what grids it supports, and this one does not support 240V delta grids. It can connect to the 208V three wire grid, or 120/208V four wire grid, but not to 240V delta. You would need to stagger three of the single phase inverters to connect directly to a 240V high leg delta grid.

Some inverters are designed with three internal units wired in a DELTA manner, and others are designed with the internal units wired in a WYE manner. In order to use similar hardware with the 277/480V counterparts, 208V inverters commonly use the DELTA arrangement, while their counterparts commonly use a 277V WYE arrangement. This way, you can standardize on hardware to work with AC waveforms in the range of 200V to 300V nominal, common for both light commercial 208V and large commercial/industrial 480V.
 
Carultch said:
This family of inverters, requires 208V phase-to-phase, and can either connect to 208V delta or 120/208 wye. Its 277/480V counterparts require a neutral and a 277/480V wye grid.

Either the datasheet or manual will spell out what grids it supports, and this one does not support 240V delta grids. It can connect to the 208V three wire grid, or 120/208V four wire grid, but not to 240V delta. You would need to stagger three of the single phase inverters to connect directly to a 240V high leg delta grid.

Some inverters are designed with three internal units wired in a DELTA manner, and others are designed with the internal units wired in a WYE manner. In order to use similar hardware with the 277/480V counterparts, 208V inverters commonly use the DELTA arrangement, while their counterparts commonly use a 277V WYE arrangement. This way, you can standardize on hardware to work with AC waveforms in the range of 200V to 300V nominal, common for both light commercial 208V and large commercial/industrial 480V.
Click to expand...


thanks for the explanation, So I can use three single phase inverter to get 240 volts across any two phases at the end. I am still confused about the neutral connection though, if we measure line to neutral connections it will still have one reading 208 volts, and the other two 120,120 volts. So will this have any effect in the performance of the inverter??I have even read about some smaller SolarEdge single phase inverter that allows no neutral connection at all. Please explain me about the neutral connection too so that i can understand it fully.
 
Designer101 said:
thanks for the explanation, So I can use three single phase inverter to get 240 volts across any two phases at the end. I am still confused about the neutral connection though, if we measure line to neutral connections it will still have one reading 208 volts, and the other two 120,120 volts. So will this have any effect in the performance of the inverter??I have even read about some smaller SolarEdge single phase inverter that allows no neutral connection at all. Please explain me about the neutral connection too so that i can understand it fully.
Click to expand...

This particular manufacturer, primarily uses the neutral connection for instrumentation purposes (i.e. as a reference point to measure voltage and phase). They also have a document you can request from them, that substantiates this, and allows the use of 705.28(C). The current is sourced onto the phase conductors, and there either is no possibility of putting current on the neutral, or that current will add up to zero by design. This is not necessarily true for inverters in general, so you'll need to confirm the specifics if it matters in your design.

To demonstrate why it is important to confirm specifics, consider an example of an inverter that has a physical basis for using the neutral. The Fronius IG-Plus 12 kW, that is now discontinued. It contained 3 internal units, that were connected from neutral to each of the three 277V phases. If you programmed it to mix-mode instead of balance-mode, the three internal units would cycle to stand-by during low power conditions. This means that when only 4 kW were available, the inverter would only operate one of the three internal units. Full current would be on Phase A and neutral, while phases B & C would temporarily have zero current.
 
Check with the utility, you may have an open delta service. I have encountered this type of service many times in Arizona and the utilities (APS & SRP) advised for the last 20 years to use single phase 240V inverters on only the 120V lines.
 
There are no 3 phase 240 volt inverters made. You can balance three single phase inverters but beware, unless you add in a phase loss relay you will fail a single phase test if the utility requires one.
 
sketchy said:
There are no 3 phase 240 volt inverters made. You can balance three single phase inverters but beware, unless you add in a phase loss relay you will fail a single phase test if the utility requires one.
Click to expand...
A quick google search turns up 3 phase delta inverters:
www.solarelectricsupply.com

Fronius IG Plus V 11.4-3 Delta 3-Phase Inverter

Wholesale 11.4 KW Three-Phase Fronius IG Plus V 11.4-3 Delta Inverter. Fronius solar inverters, low prices. Complete systems available. Fronius Authorized.
www.solarelectricsupply.com www.solarelectricsupply.com
I would either change the inverters to 3 phase delta 240 or change the service to 208Y.
 
synchro said:
A 240V delta to 208V wye transformer such as this one would help:

store.maddoxtransformer.com

3-Phase 240V Delta - 208 Y 120

This transformer is designed to convert 3-phase 240v to 3-phase 208 Y 120 to run equipment such as panels, motors, CNC machines, welders, conveyor systems, pumps, printing equipment, fabrication tools, and other business machines. Primary Voltage: 240 Delta Secondary Voltage: 208 Y 120...
store.maddoxtransformer.com store.maddoxtransformer.com
Click to expand...

Thank you, looks like this would be the best solution rather than switching to three single phase inverter
 
BillK-AZ said:
Check with the utility, you may have an open delta service. I have encountered this type of service many times in Arizona and the utilities (APS & SRP) advised for the last 20 years to use single phase 240V inverters on only the 120V lines.
Click to expand...
this was my first time with high leg issues, in fact this issue helped me to understand a lot, in then future I will make sure to contact utilities to identify but right now i am sticking with the transformer , but that was good idea too.
 
Designer101 said:
this was my first time with high leg issues, in fact this issue helped me to understand a lot, in then future I will make sure to contact utilities to identify but right now i am sticking with the transformer , but that was good idea too.
Click to expand...

You should really follow Bill's advice and contact the utility to make sure you can backfeed the high leg before you buy the transformer. For these kinds of projects interconnection applications should be filed before you build.
 
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