using grid-connected inverter with open-delta 3-phase configuration

[PG1995]

Hi

My friend needs to install a grid-connected PV inverter. The mains are open-delta 3-phase 240V (it might be 208V, I would conform it soon) configuration. Could you please tell me that if it's possible to connect an inverter to an open-delta mains? The electric utility wouldn't have any problem.

I need to find an appropriate inverter. I was able to find that SMA-America manufactures inverters which could be used with open-delta as is **broken link removed**. I wasn't able to find one from **broken link removed**. An inverter from Fronius would be preferred. Thank you.

Regards
PG

Helpful links:
1: https://www.pumpsandsystems.com/topics/pumps/pumps/why-wye-why-delta (it shows different configurations such as center-tapped delta, center-tapped open delta, open delta)

 

[MrAl]

Hi,

When i worked in the industry we did three phase systems all the time, up to maybe 30kw.
But most of them were wye, and i only remember a few deltas of any kind, and i dont remember how we did the 3 phase inverters for solar applications (line tied) other than most of them were wye.
The wye's were 120v line to neutral, and 208v line to line (120*sqrt(3)=208).
I actually dont remember what the delta's where, but we could look it up.

But if you found one that 'works' with the system you need it to work with, why would you be asking this question...wouldnt they be able to tell you better if they actually make one already, and shouldnt it actually work with what they say it will work with?

 

[KeepItSimpleStupid]

There is a high-leg delta. https://en.wikipedia.org/wiki/High-leg_delta

An electrician might be able to do a delta-Y transformation with transformers for the inverter.

 

[BobW]

Open delta should be 240 volts. I've never seen a 208V open delta. It would require a pair of very strange transformers for 208.

If you can drive two single phase 240 volt inverters from your solar panels, it should be possible to wire them, open delta, to the grid and they should synchronize independently.

 

[PG1995]

Thank you, everyone.

MrAl, I have sent an e-mail to Fronius but they haven't responded yet.

KISS, recently I was reading about delta system just to get the basics. You might find the links given below interesting.

Open delta should be 240 volts. I've never seen a 208V open delta. It would require a pair of very strange transformers for 208.

If you can drive two single phase 240 volt inverters from your solar panels, it should be possible to wire them, open delta, to the grid and they should synchronize independently.

Thanks. Would it be possible for you to show me a schematic or link me to some source?

Regards
PG

Helpful links:
1: (Delta 3-phase system)
i: https://en.wikipedia.org/wiki/High-leg_delta
ii: **broken link removed** (shows different form of delta configuration)
iii: https://www.electriciantalk.com/f2/explain-stinger-high-leg-23606/ (high leg, stinger, etc.)
iv: https://control.com/thread/1026198752 (might be good; didn't read carefully)
v: https://www.electro-tech-online.com/attachments/highlegdelta-jpg.92158
vi: https://www.pumpsandsystems.com/topics/pumps/pumps/why-wye-why-delta (good one)

 

[KeepItSimpleStupid]

I lost my text book with all my electrical/power stuff. I should say stolen, but it wasn't quite that either. maybe locked out and then stuff disposed of.

One lab I worked in had the high leg delta, but it was unimportant to be then. When we moved the guys in charge couldn't specify power correctly, so for 240 equipment we has 208V now and for systems that required L1, L2, G and N; Neutral was missing.

Later, I found potentially 470 outlets that were bad from the manufacturer after the warranty was up. More like: expensive equipment got destroyed and I wanted to know why.

AND we were assured we would have a cooling loop. Well, they tried to force 90F water from a 12" main through a 1/4" tube, so that didn't work well. It was supposed to be 55 F clean water. SO, the new equipment got connected to filters and drains. Luckily the drains were installed.

To make an isolated pad, you pour the entire pad. Cut and dig out the isolated portion and then poor it.

 

[BobW]

Would it be possible for you to show me a schematic or link me to some source?

I wasn't thinking of any specific product, but if you have two single phase inverters that are designed to be synchronized to the grid, then I can see no reason why you couldn't connect their outputs in open delta fashion, as long as the inverter outputs are isolated from ground. They would essentially be independent of each other, and each one would synchronize to the phase that it is connected to. However, having said that, I would still recommend that you check with the manufacturer.