Line current. Wye inverter to Delta service

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
Do we agree on the following? Three single phase inverters connected to a three phase system as in post #14. Say its a regular 208 service. Inverters are thus 208V, say 32 amps. That is 20KW total of inverters (208)(32)(3). Three phase power is W=(V)(I)(1.732) so current is 55.5 A or 1.732 times the inverter or phase current. The currents I am referring to as being different are the 32 amps and the 55.5 amps. (phase and line respectively). Are we each talking about different currents or points of measurement?
Say you have two 100kW 3P inverters, one connected wye and the other connected delta, both running at capacity. You put your clamp ammeter around the output conductors (one at a time, of course) and take measurements. Do you see a difference in current between the conductors from the wye inverter and those from the delta inverter? I don't think you will. There are inverters that can be connected either way and they don't quote different output current or required OCPD for the different connections.

It's why I mentioned semantics; the current in those conductors is what I know as "phase current" and it's always the same as line current for a balanced 3P circuit in the same way that the current in both conductors in single phase 240V is the same as the line current; maybe the term means something else to you.
 
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Say you have two 100kW 3P inverters, one connected wye and the other connected delta, both running at capacity. You put your clamp ammeter around the output conductors (one at a time, of course) and take measurements. Do you see a difference in current between the conductors from the wye inverter and those from the delta inverter? I don't think you will. There are inverters that can be connected either way and they don't quote different output current or required OCPD for the different connections.

It's why I mentioned semantics; the current in those conductors is what I know as "phase current" and it's always the same as line current for a balanced 3P circuit in the same way that the current in both conductors in single phase 240V is the same as the line current; maybe the term means something else to you.
Ahh ok I think I see where the misunderstanding is. For the purpose of this thread when we are talking about "delta connected" or "wye connected" we are NOT referring to the type of three phase system that the inverters are interconnecting to. We are talking about connecting three single phase inverters in a delta or wye configuration (mostly delta, forming a wye connection from three single phase inverters would be odd and maybe not even work).

Regarding "phase" vs "line" values, again these are well established and not semantic. I believe you are incorrect to interchange phase and line (although in a wye connection line current is the same as phase current but not in a delta). I think if you google a few articles or look at a text you will see what I mean.

https://www.allaboutcircuits.com/tex...onfigurations/

Edit: perhaps reread my post #16. That example has the different phase and line currents.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
...forming a wye connection from three single phase inverters would be odd and maybe not even work.
It does work, or at least it did with the old style transformer coupled inverters. I did it several times back in the day. Not lately, though; there are a lot more smaller 3P inverters available now than there used to be. Granted, I haven't tried it with transformerless inverters, but I did build a system that way with (42) 6000W Sunny Boys - fourteen of them per phase connected phase to neutral on a 480v 3P service.

And if you will reread the OP, he was talking about a single inverter, not three single phase inverters. The output current from a single three phase inverter is the same per phase conductor and the same as the line current whether it is connected to a delta or wye service. I think that was his question.
 
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And if you will reread the OP, he was talking about a single inverter, not three single phase inverters. The output current from a single three phase inverter is the same per phase conductor and the same as the line current whether it is connected to a delta or wye service . I think that was his question.
Yes I absolutely agree with the red. Most of the confusion here comes from using "delta" and "wye" in different contexts. One use is the type of electrical service, specifically the transformer connection serving the service. The second is the connecting of three single phase sources/loads/inverters into delta and wye configurations and the resulting current and voltages "seen" by the single phase components. The latter is what I was talking about during out back and forth and for that topic "Phase" and "line" have specific meanings. For the former, say, a three phase feeder, "phase current" vs "line current" are essentially synonyms. For a three phase plus neutral circuit, (from a wye) "phase voltage" probably technically means the line to neutral voltage but as far as i know no one really says that and I wouldnt use it. That is my analysis anyway.

It does work, or at least it did with the old style transformer coupled inverters. I did it several times back in the day. Not lately, though; there are a lot more smaller 3P inverters available now than there used to be. Granted, I haven't tried it with transformerless inverters, but I did build a system that way with (42) 6000W Sunny Boys - fourteen of them per phase connected phase to neutral on a 480v 3P service.
Ok cool. But for some reason when I said "wye connected" I was thinking of a three inverters wye connected with only the three phases connected and the star point isolated. That is what I was questioning as to whether it would work. Connecting single phase inverters line to neutral to a three phase system is fine other than the voltages that would be required, 120V or 277 volts and I am not aware of any currently that have that voltage options.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
Yes I absolutely agree with the red. Most of the confusion here comes from using "delta" and "wye" in different contexts. One use is the type of electrical service, specifically the transformer connection serving the service. The second is the connecting of three single phase sources/loads/inverters into delta and wye configurations and the resulting current and voltages "seen" by the single phase components. The latter is what I was talking about during out back and forth and for that topic "Phase" and "line" have specific meanings. For the former, say, a three phase feeder, "phase current" vs "line current" are essentially synonyms. For a three phase plus neutral circuit, (from a wye) "phase voltage" probably technically means the line to neutral voltage but as far as i know no one really says that and I wouldnt use it. That is my analysis anyway.
You see? We agreed all along. :D
 
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