I need some help designing 3 phase system. please

dieselenvy

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I had a local supplier of Jinko panels message me. At 67c per watt they are a bit more expensive than some other panels I was looking at but it seems most of the Jinko panels meet the PID requirements.

I've been learning more about the 120/208 three phase. It seems like most 240v appliances will run on 208v. So that may be the best route like you said.

Will 1 or 2 of the SB10000TL-US work AC coupled to the SI 6048 since they can only accept 6700 w AC input each or are they a little higher than the 5048. I don't really quite understand how the 208v AC out of the SB works. Is 2 hots of 120v that are 120% out of phase? How do they connect and work exactly with SI in a phase orientation? From the diagrams I see they connect in the sub-panel but I don't understand exactly how that works.

My genny plug is an L6-30 if that helps any.
 

Hedges

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Yes, most things should work on one or two legs of 120/208Y. 240V heating appliances will draw a bit less power. Motors may draw a bit more current for the same load (or maybe at less than full load will have better power factor?) What wouldn't work is a 120/240V autotransformer or two 120V transformer primary windings with neutral also connected.

L6-30, 3 wire ground/hot/neutral (or ground/hot/hot), 30A 250V



Does your generator also have 120V outlets? If so you should be able to install a 4-wire split-phase outlet.
The 3-wire outlet with ground should not be used for neutral and two hots, even if the source has a grounded centertap, because your loads could get electrified ground.

If it only has 240V and no center tap, a transformer could be used to produce either split phase or full wattage at 120V.


If you were to use the system to backfeed into the grid (or backfeed into grid connected main panel, but with a zero-export configuration using current transformer to sense), there is a 56A limit per Sunny Island (that's the 6700W limit, at 120V). Perhaps there is some way to have a device control Sunny Boy's power output while grid feeds 60 Hz through Sunny Island to Sunny Boy; I think they do that at least with some newer models.

If you tell Sunny Island not to backfeed the grid, it can treat grid same as it would a generator - connect when it wants power, disconnect when PV output exceeds loads and battery charge needs so nothing backfeeds. In that case you can have 10kW of Sunny Boy per SI-5048US or 12kW of Sunny Boy per SI-6048US.

About the only difference between the two is 6048 seems to be a bit more efficient, can output 5750W continuous at 25 degrees C while 5048 can output 5000W. Both have same surge capability. 6048 has larger battery terminal, while 5048 has smaller double terminal.

With 2x SI (either model) wired 120/240V split-phase, you could have 1x 10000TL-US-12 (240V model) backfeeding grid, or 2x 10000TL-US-12 not backfeeding grid.

With 3x SI (either model) wired 120/208Y 3-phase, you could have 3 x 6700W = 20,100W, 2x 10000TL-US-10 or 10000TL-US-12 backfeeding a 3-phase grid. (I think; they have to rearrange watts between legs to do that.) With 3x inverters not over 6700W each, could do the same.

If you set up a 120/208Y 3-phase system and feed it 120V single phase, you would be limited to 6700W backfeed. I haven't figured out yet if 4x SI can be wired 120/208Y with two in parallel for 13,400W to/from grid.

If you use the grid only as a generator, don't backfeed, then you can have 3x 10000TL-US (either model because both do 208V) for 30kW of GT PV on your 120/208Y island grid.

Oh, the 10000TL-US has a firmware bug that grid-backup mode doesn't curtail production. SMA investigated my inquiry and told me to set it to off-grid while using it on grid behind Sunny Island, with the Sunny Boy backfeeding the grid. I suggest you do not do that unless they give you such instructions in writing; it differs from what documentation says to do. I used it that way for a while then replaced with 5000US. I felt there could be a safety issue that SMA Germany foresaw but SMA support in U.S. didn't know about.

Two 120V hots 120 degrees apart in phase is 208V. With just one Sunny Boy across L1 and L2, nothing on L3, it drives current with a phase shift. Same with two Sunny Boy. Three Sunny Boy distributed across all three pairs, and they add up to in-phase current on each line.

On SMA's site, I'm only finding a newer document without older models listed. Download and save the following:



I just got my 3-phase setup running. 3x SI-5048US wired 120/208Y, old tired 100Ah 48V battery bank (4x 12V batteries), 30A dryer cord feeding master SI, 3x auto-transformer 120/277V (actually a bit low, 120/260V) making 277/408Y (actually 260/450Y), one Sunny TriPower 30000TL. Just one 2500W PV string so far, about 380Vmp.

It does transfer power on all three phases and exports to grid over the one connected 120V 30A line. When I disconnect grid with battery full, SI raises frequency to 60.5Hz and TriPower disconnects. I haven't connected a data cable yet. It has SpeedWire (Ethernet) installed, and I've ordered a RS-485. The TriPower is supposed to support UL-1741-SA and off-grid. No parameters whatsoever in the manual, will have to see what is there when I get it talking.

One weirdness is my Harbor Freight clamp meter shows current in the 120V legs, e.g. 0.50A with sun low and clouds. But on the 277V legs it shows zero. Using DC setting I do see current in the PV wire.
 

dieselenvy

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Yes my gen has two 20amp 120 outlets. I understand on what you are saying. Swap my 3 wire plug for a 4 wire, that makes sense.

Most all of the "weird" transformers I try to look up are super expensive. How much did you spend for 3x transformers 277 to 120?

I called SMA tech support to try and get a bit more info. This is probably something you have already covered but bare with me.

They said I will have to contact inside-sales to get the reason why but that the  Sunny Boy 10000TL-US (10&12 I think) have been discontinued and won't work with grid tie, only off grid. Here is a link he sent me.

https://files.sma.de/downloads/SB-OffGrid-TI-US-en-22.pdf

They said I will need 3 SB 208v to work with 3 SI 120/208v and I can feed them up to 36kw AC coupled. So all that looks good. Just that for some reason it won't work if I connect to grid. If or when I get grid power down the road. So I'm not sure where that leaves me. Maybe back to the tripower idk.

I contacted "thepowerstore" with some SMA questions and they wanted to steer me toward the Sol-arks because ease of install, saying they sell 250 to 1 sol-ark vs SMA. But I can't justify spending $21k on inverters for 3 phase.

Amazon sells a comparatively cheap Digital phase shifter. I'm not sure how well they work.

 

Hedges

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Is that 3-phase converter a VFD?
What is its Power Factor? Is it PF corrected?
Poor power factor will upset AC coupled inverters like Sunny Boy.

The 10000TL-US will work on-grid (UL-1741) and will work off-grid (wider voltage & frequency, and ramps down power output as frequency increases.
Even if wired with RS-485 to Sunny Island, and it switches from "on-grid" to "grid-backup", it fails to implement ramp down of power with frequency. I told SMA about that, which they acknowledged after reviewing firmware and change list of compatible inverters.
But you should be able to use grid as generator, telling Sunny Island never to backfeed. It only connects to grid when battery is low and PV doesn't supply enough power.
I think a 3-phase Sunny Island system will work with any number of Sunny boy, not just multiples of 3. I'll be trying that one of these days. I know it works with grid feeding just one leg.
If 36kW of Sunny Boy and 18kW of Sunny Island, there may be some conditions where it can't process all PV input; Sunny Island has to take power from some legs and send to others.

I paid about $300 plus $250 shipping for one 9kVA toroid, which has 2x 88V/120V windings and 1x 208/240V winding.
Then I found two more at a surplus store for $25 each.
I was able to wire them as 120/260V auto-transformer. I think I could also use two of them to create a 3rd leg from two legs of 120/208Y.

I'm looking for some other transformers but all on eBay are East coast, several $hundred shipping, and no two alike. Prices are $200 to $900 each. I'd rather pay $200 and get locally.
I would like 3x 480/240 to 240/120, or 277 to 120, 10kVA. Also want 1x 25kVA but might get by with two more 10kVA.

If you get a TriPower like I did, you'll probably spend in transformers what you saved in inverter cost. Make the most sense if you have 480V 3-phase already. (the smaller 15000TL through 24000TL require 277/480Y. The 30000TL I got is OK 480 Delta.

If those 208V only 10000TL-US-10 are still available for a good price, those should work off-grid, and on-grid if you have 208V utility service. If you are feeding 1 leg of 120/240V utility into 1 Sunny Island of a 120/208Y system, then can't have more than 6.7kW of Sunny Boy on Sunny Island if it allows backfeeding.
A 10000TL-US-12 supports 208/240/277V so could be moved to 120/240V grid.

What you could do for now is assemble 3-phase Sunny Island system with several Sunny Boys that support 208/240V. That runs your motors. If you later get 120/240V grid, use VFD or converter to drive motors directly from grid. Reconfigure Sunny Island (2 or 4 of them) for 120/240V. If you want to backfeed grid, limit is 6.7kW per Sunny Island.
 

dieselenvy

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I think a 3-phase Sunny Island system will work with any number of Sunny boy, not just multiples of 3.

So I wouldn't AC couple 3 SB 10k 208v to 3 SI6048? Why is that?
 

Hedges

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Yes, 3x 10kW 208V Sunny Boys is a good fit for 3x SI6048.
Or 6x 6.0 SB -40 or -41 (current model)

(I said, "not just", did not say "just not". Should work with 0, 1, 2, 3 of the 10k units.)

It should also keep working if a Sunny Boy fails. It will also keep working for single-phase household loads if a Sunny Island fails.
With a couple transformers I could make 3-phase from two Sunny Islands.

Only if you let it backfeed into grid does the 56A relay limit apply.


I'm planning to wire a thermistor to one of the Sunny Island slaves, install RS-485 and sockets. I would like to be able to swap a couple plugs and reconfigure if the master goes down.
 

dieselenvy

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I ran across this SMA SI webinar and I'm concerned a bit about a cluster of SI's only being able to work with up to 3 batteries otherwise facing potential equalization issues . I am actually planning to build a 42ksih KW battery pack consisting of 3p 16s 280ah CATL LIPO cells. But I don't like the fact that I can't increase the battery size if needed.

 

dieselenvy

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Yes, 3x 10kW 208V Sunny Boys is a good fit for 3x SI6048.
Or 6x 6.0 SB -40 or -41 (current model)

(I said, "not just", did not say "just not". Should work with 0, 1, 2, 3 of the 10k units.)

It should also keep working if a Sunny Boy fails. It will also keep working for single-phase household loads if a Sunny Island fails.
With a couple transformers I could make 3-phase from two Sunny Islands.

Only if you let it backfeed into grid does the 56A relay limit apply.


I'm planning to wire a thermistor to one of the Sunny Island slaves, install RS-485 and sockets. I would like to be able to swap a couple plugs and reconfigure if the master goes down.
I'm not sure if you saw my last post but I was able to get two new open box 6048 for $5k plus shipping. I'll let you know how the install goes. cheers
 
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Hedges

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I haven't worked with lithium batteries and BMS on Sunny Island.
Lead-acid of course would have multiple banks paralleled, and to SI it is just more Ah.
With BMS, SI would talk to them all (unless one is master, others are slaves.)
Battery capacity limit would see to then come from cell size (unless multiple cells are in parallel on a single BMS.)
 

Seven30

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Ill be looking for some similar 3phase solution soon. In my case 3phase grid power is not an option.

While there are many inverter systems than can function in 3phase mode all I have found must stay in inverter mode.
That is they CANNOT take two phase 240 and pass through as 3phase.

The charger would have to be able to support the average inverter input loads even with a good sized battery.

The alternative would a two phase setup feeding something like a perfectphase digital 3phase synthesizer.

Still 15kw of inverter power with batteries is a big system if you intend to run it for any length of time.

Im my case I just need 30 minutes of reserve to shut things down in case of power failure.
 

dieselenvy

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Ill be looking for some similar 3phase solution soon. In my case 3phase grid power is not an option.

While there are many inverter systems than can function in 3phase mode all I have found must stay in inverter mode.
That is they CANNOT take two phase 240 and pass through as 3phase.

The charger would have to be able to support the average inverter input loads even with a good sized battery.

The alternative would a two phase setup feeding something like a perfectphase digital 3phase synthesizer.

Still 15kw of inverter power with batteries is a big system if you intend to run it for any length of time.

Im my case I just need 30 minutes of reserve to shut things down in case of power failure.


I ended up buying 3x SI and 3x SB and 20kw of solar. I would only run heavy loads during the sunshine hours or with genny running. I know it would suck the batteries down super quick otherwise.
 

Hedges

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While there are many inverter systems than can function in 3phase mode all I have found must stay in inverter mode.
That is they CANNOT take two phase 240 and pass through as 3phase.

The charger would have to be able to support the average inverter input loads even with a good sized battery.

My Sunny Island master takes in single-phase 120V, passes it through to L1 of 3-phase. It charges the battery while the two slaves invert to create L2 and L3.
This works for power from grid to load, or from Sunny Boy/Sunny TriPower back to grid, up to 6700W. More GT PV than that would exceed pass-through relay capacity, so couldn't be set up to backfeed, would have to treat grid as generator.
 
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