3 1-phase inverters connected to each 3-phase supply.

[Karezo]

I am very new to this industry, so please bear with me. I'm wondering if this setup is possible. Assuming all appliances within the system are single phase, I believe they wouldn't be affected by unbalanced supply/distribution between the 3 phases. But what would be the disadvantages here?

 

[ggunn]

I am very new to this industry, so please bear with me. I'm wondering if this setup is possible. Assuming all appliances within the system are single phase, I believe they wouldn't be affected by unbalanced supply/distribution between the 3 phases. But what would be the disadvantages here?

Yes, it is possible to connect three single phase inverters to a three phase service, within some constraints. Most often it's phase to phase - AB, BC, and CA.

 

[pv_n00b]

This used to be the usual way to do it for smaller 3-phase systems back when the smallest 3-phase inverter was over 200kW. Try to use three inverters of the same rating. In a small number of cases, an AHJ would give grief over 705.40 and how loss of a phase should disconnect all the inverters. But that is rare.

 

[Karezo]

Thanks for answering guys. I have another one though, what if I connect one 1-phase inverter to a 3-phase system?

I've searched online but I can't find if it should be connected A-B or A-N or if it even has any disadvantages.
Thanks again in advance!

 

[ggunn]

Thanks for answering guys. I have another one though, what if I connect one 1-phase inverter to a 3-phase system?

I've searched online but I can't find if it should be connected A-B or A-N or if it even has any disadvantages.
Thanks again in advance!

This is most often done on 240/120V high leg services connected A-N-C where B is the high leg. There are a few such services around on older residential properties; otherwise, most three phase services are large and most single phase inverters are small, so I don't know why anyone would want to do this.

I hope your interest is merely academic; this kind of thing should only be done by an experienced PV designer/installer.

 

[BackCountry]

Thanks for answering guys. I have another one though, what if I connect one 1-phase inverter to a 3-phase system?

I've searched online but I can't find if it should be connected A-B or A-N or if it even has any disadvantages.
Thanks again in advance!

While you could do this, the bigger question is will your utility approve your interconnection.

If it was small scale, and you’re on a true three phase system, not a high leg delta, then I’d rather see you use micro’s and phase balance them.

If it’s high leg, then you’d want to backfeed just the single phase pot — and again: you’d need to check with your utility first on interconnection requirements, and transformer sizing. Most of the time a high leg setup is for a well, and the tx size can be small (like 10kva) don’t get caught without having checked this first.

If it’s 208Y/120V, there are small size inverters available for that voltage: Enphase, SolarEdge, etc.

 

[Karezo]

I hope your interest is merely academic; this kind of thing should only be done by an experienced PV designer/installer.

It is don't worry. hahaha I will still consult experienced engineers on site if ever these situations come.

While you could do this, the bigger question is will your utility approve your interconnection.

If it was small scale, and you’re on a true three phase system, not a high leg delta, then I’d rather see you use micro’s and phase balance them.

If it’s high leg, then you’d want to backfeed just the single phase pot — and again: you’d need to check with your utility first on interconnection requirements, and transformer sizing. Most of the time a high leg setup is for a well, and the tx size can be small (like 10kva) don’t get caught without having checked this first.

If it’s 208Y/120V, there are small size inverters available for that voltage: Enphase, SolarEdge, etc.

Thanks for the explanation!