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3-phase system?

chetwynd

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I have a small orchard with a 15 HP 3-phase well pump here in California. Power goes pole to meter to service panel, to pump. PG&E tells me it's 4-wire, 3-phase, 240v. I have no yet verified that with my tester.

I’m going to install a small solar system relatively quickly to get grandfathered into NEM 2.0, before new systems lose their ability to earn back anywhere near their cost. Then later on deal with adding capacity.

Anyway, what are my options for 3-phase? I own and am familiar with a standard 240v residential system, but 3-phase is new to me.

My options as I see it are panels with Solar Edge optimizers going to a Solar Edge 3-phase inverter. Or, since it's 240v do I even need to deal with a 3-phase inverter?

Or another brand without the whole optimizer scheme.

What are your thoughts?

Thank you
 
I've done dozens of small orchards in CA just like yours. When they say it's 4-wire, 3-phase, 240V, you need to verify if the Neutral (N) 4th wire is bonded to ground in a WYE, and not a 120/240/208V Stinger, which is also 4-wire, 3-phase, 240V, but not a Wye. It has a center tap on one side of a delta, that is grounded to give 120/120 from A to N to C, and 208 from B to N. It's also referred to as a high-leg delta and these are common on rural pole mounts.

1. If it is a WYE, then all you need is an auto-transformer, 277Y/480V, 3Ph to 138Y/240V, 3Ph.
2. If it's a Stinger (or a WYE) then you need an isolation transformer, 277Y/480V, 3Ph to 240V Delta 3Ph.

In both cases, the following inverter connects to the 480V side.

The inverter of choice for me is a CPS 25kW, 480VAC, 1000VDC. They are inexpensive and very reliable, and their support in the valley is excellent. I would not recommend going 1-phase or SolarEdge. IMO and experience, they fail often.

The CPS doesn't require optimizers, and it has multiple MPPT inputs so you can expand the capacity up to 25kW+ on the DC side.

Also, PG&E will probably make you upgrade the meter cabinet and add a 3Ph disconnect switch, per Rule 21. All equipment, including the transformer, need to be outdoor rated, NEMA 3R.

Good luck.
 

SMA and Fronius would be tier-one manufacturers with a good reputation, for GT PV inverters.

There are Chinese brand inverters offering PV, battery backup, 3-phase. If you can find one that is UL listed (including latest -SA requirements), the functionality/price might make it worth trying.

Several brands of battery or hybrid inverters should be configurable for 3-phase. Schneider, Sol-Ark, Outback (don't know if they have UL-1741-SA). See if Midnight Rosie is available yet. SMA Sunny Island + Sunny Boy would work for 120/208Y, but don't know if SI not being -SA will cause any permitting issues.


1. If it is a WYE, then all you need is an auto-transformer, 277Y/480V, 3Ph to 138Y/240V, 3Ph.
2. If it's a Stinger (or a WYE) then you need an isolation transformer, 277Y/480V, 3Ph to 240V Delta 3Ph.

In both cases, the following inverter connects to the 480V side.

The inverter of choice for me is a CPS 25kW, 480VAC, 1000VDC. They are inexpensive and very reliable, and their support in the valley is excellent.

Got links to particular transformers you find work? If his case is 240V (more or less) grid and he needs 277/480Y to excite the inverter, that is step-up for the grid tie application. But you mention an isolation transformer 277/480 to 240 delta, which would be step-down.

From my experience, only some transformers are reversible. I think heavier may work, but lighter weight and designed to the hairy edge, they do not:


I would not recommend going 1-phase or SolarEdge. IMO and experience, they fail often.

Solar Edge, I'm seeing and hearing similar.

1-phase - do you think your 3-phase solution is more reliable than Sunny Boy?
I think they are very good, although I like the idea of 3-phase GT PV because approximately zero ripple current from caps.
At least with 3x single-phase inverters, if one fails you still have 2/3 output while getting it repaired.
My experience operating SWR2500 for 17 years shows 34 year MTBF.
 
Thank you guys for your responses. Let me process all of that. I don't live at the property but I can go put a tester on it. Maybe this photo helps? This is my panel.
 

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One more, bigger view.
 

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Zooming in, I see the component supports a range of voltages
You really need the actual voltage.

NC Solar recommends 3-phase (which I like), but I recommend an inverter that can be used without a transformer.
 
With a neutral coming from the meter, it appears to be a wye system. And the contactor has a 220v coil. So I would guess it is a 208/120v system.
But, it's still just a guess.
 
OK, if 120/208Y then 1, 2, or 3 single-phase Sunny Boy could be used:


These (or other UL-1741-SA) inverters could work with Sunny Island if battery backup was desired in the future.
A 15 HP pump might or might not be too large for that to start.

Anybody know of a good 3-phase GT PV inverter for that voltage?
A UL listed hybrid (preferably batteries optional)?

But he said PG&E told him it was 240V, which would still work with single-phase inverters.
The older Sunny Boy auto-distinguish 208 from 240V when a neutral is connected. Would have to manually configure for 240V and leave neutral disconnected if 240V delta (or equivalent Y). Need to confirm these newer -41 models also allow that. Newer code has called for neutral connection, which would tip off the inverter this supply is something different.
 
I'll go tomorrow and get some more information on the voltage. I really appreciate everyone's input here!
 
Zooming in, I see the component supports a range of voltages
You really need the actual voltage.

NC Solar recommends 3-phase (which I like), but I recommend an inverter that can be used without a transformer.
You won't find a 3-phase 240V inverter. They come in 208V or 480V. The 480V is cheaper and more common.

Also, the SMA Sunnyboy is okay, but you will pay 2x the cost for it compared to the CPS I recommended. It would cost way more than that if you choose to do it with three 1-phase inverters to use 240V. The CPS I suggested has the best reputation and lowest cost. The company "Solectria/Yaskawa", private label the CPS inverters, and I've had my crews install hundreds of them across CA. They have very good support in the Valley.
 
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With a neutral coming from the meter, it appears to be a wye system. And the contactor has a 220v coil. So I would guess it is a 208/120v system.
But, it's still just a guess.
Very unlikely for it to be 208V and PG&E to call it 240V. Also, having a Neutral doesn't mean it's a WYE. It could be a High-leg Delta "Stinger", like this. These are usually what are referred to as 240V, 4-wire, 3-phase in the Valley. You can't connect ANY 3-phase inverters directly to this, they will have ground-fault issues immediately. It requires an isolation transformer, every time.

1200px-High_leg_delta_transformer.svg.png
 
Very unlikely for it to be 208V and PG&E to call it 240V.

View attachment 123618

If it is this configuration, with 120/240V split-phase L1/N/L2, then you can ignore L3 and just do a split-phase configuration like almost all home systems. Many to choose from. Your motor will draw balanced power and utility drop will carry imbalanced power, but not your problem. You may even deliver net power on L1 and L2 while drawing the same power on L3.

I do prefer 3-phase, and it can be cheaper per watt, but if a transformer is required that adds cost. Step-down from 3-phase 480V to 208V is readily available, probably also to 240V. But step-up is harder to find, may have to buy new for a couple $thousand. I think consumer commodity split-phase inverters are the way to go, when you're just connected to the grid and not battery backup.

I would suggest a pair of these, 15kW for $3200, but you need to find them in stock somewhere:


I’m going to install a small solar system relatively quickly to get grandfathered into NEM 2.0, before new systems lose their ability to earn back anywhere near their cost. Then later on deal with adding capacity.

Probably, only the watts you have at time you get utility permission to operate will be grandfathered under NEM 2.0, and additions would have to be under NEM 3.0

If you can get the panels and connect them somehow, maybe a flat "deck" on the ground with fence around? complete in time for NEM 2.0

Arrays of two orientations should flatten production during the day, rather than peaking at noon (export to grid) and drawing other hours. If you add capacity parallel to the motor itself, behind any float/pressure/irrigate switch, it will only produce while motor draws power, preventing excess export. So that way you might get away with added capacity without needing new permission. But would waste any production when motor not running.

An active "export limit" system would let added capacity fill in allowed export for more hours of the day.
 
Man you guys are electrical BEASTS and I mean that in a very complimentary way. I'm going to go this morning to look at voltages and will report back ASAP. Stay tuned, you guys are all warmed up now!
 
L1 to L2: 240
L2 to L3: 240
L1 to L3: 240

L1 to ground: 120
L2 to ground: 120
L3 to ground: 208
Neutral and ground on the same bar as shown in earlier photos.
 
Just like the drawing NC Solar showed.

I'm not sure if its true no 3-phase inverter can be used without transformer, but that's what NC said, and unless you find one spec'd for high-leg, probably true.

How many kW of PV do you want to install?
I think any inverter for 120/240V split-phase household power should work.
I use Sunny Boy, but there are many choices. Unfortunately, probably need recent model compliant to UL-1741-SA (no old models). Check the CEC website, make sure the one you select is on approved list.
 
L1 to L2: 240
L2 to L3: 240
L1 to L3: 240

L1 to ground: 120
L2 to ground: 120
L3 to ground: 208
Neutral and ground on the same bar as shown in earlier photos.
Yup, a Stinger, just as I suspected.
I have a solution for you, easy peasy, no transformer. Using microinverters. Bingo! I'll PM you.

Screen Shot 2022-12-08 at 1.15.42 PM.png
 
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L1 to L2: 240
L2 to L3: 240
L1 to L3: 240

L1 to ground: 120
L2 to ground: 120
L3 to ground: 208
Neutral and ground on the same bar as shown in earlier photos.
That's a 3 phase high leg Delta configuration.
Would have known that, if the center leg was identified as it should be.
Things just got trickier. 3 phase inverters won't like this. It will require an isolation transformer.
 
Yup, a Stinger, just as I suspected.
I have a solution for you, easy peasy, no transformer. Using microinverters. Bingo! I'll PM you.

Diagram says, "brown - Line. blue - Neutral"
How does that work with stinger?
If those were isolated 240V inverters, could go line to line.
If 120V, I assume you only put on the two 120V lines, not the stinger.

Probably 240V string inverters could also work line to line, but only on the two sides with stinger if their EMI and transient protection components can take it. Some can take 277V, so 208V to neutral would be fine (just different max wattage.)

For home installations, microinverter takes care of RSD and arc-fault requirements, which add cost to string inverter systems now that they're required.

OP's is agricultural, so with a ground-mount array those safety features aren't required. Offers more economical solutions.
 
Diagram says, "brown - Line. blue - Neutral"
How does that work with stinger?
If those were isolated 240V inverters, could go line to line.
If 120V, I assume you only put on the two 120V lines, not the stinger.

Probably 240V string inverters could also work line to line, but only on the two sides with stinger if their EMI and transient protection components can take it. Some can take 277V, so 208V to neutral would be fine (just different max wattage.)

For home installations, microinverter takes care of RSD and arc-fault requirements, which add cost to string inverter systems now that they're required.

OP's is agricultural, so with a ground-mount array those safety features aren't required. Offers more economical solutions.
The HM-1500NT is a 240V isolated 4-in-1 microinverter. You can connect 3 of them as a 240V delta with 12 solar panels and a disconnect switch. No transformer is required.
 

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