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I'm using 2-STP20000TL inverters that have 480/277 terminals. The 50 Kva, 480 Delta, 208/120 transformer will not (I assume) have a neutral terminal. How would one wire this?
I'm using 2-STP20000TL inverters that have 480/277 terminals. The 50 Kva, 480 Delta, 208/120 transformer will not (I assume) have a neutral terminal. How would one wire this?
I'm using 2-STP20000TL inverters that have 480/277 terminals. The 50 Kva, 480 Delta, 208/120 transformer will not (I assume) have a neutral terminal. How would one wire this?
This situation seems to come up quite often and I always wonder why the choice is made to deal with transformers rather than spec inverters that match the electrical service? Just out of curiousity, what are your reasons, or did you not design the system?
This situation seems to come up quite often and I always wonder why the choice is made to deal with transformers rather than spec inverters that match the electrical service? Just out of curiousity, what are your reasons, or did you not design the system?
Partly it's because there is little overlap between native 480 and 208 inverter sizes. That's getting better, though. I ran into it once because we got a contract to build 11 systems for a single customer and only one of his sites had a 208V service, and we got a good deal on 480V inverters because we bought a boatload of them.This situation seems to come up quite often and I always wonder why the choice is made to deal with transformers rather than spec inverters that match the electrical service? Just out of curiousity, what are your reasons, or did you not design the system?
Plus you have the opportunity for 1000V systems on the DC side, that are seldom possible with 208V systems.
50 Kva, 480 Delta, 208/120 transformer will not (I assume) have a neutral terminal. How would one wire this?
50 kVA is not a standard 3-phase size. 45 kVA is the closest.
You might be able to use a 45kVA- SMA says the inverter kVA has to be 90% of the xfmr size, so 40kVA plus 10% = 44kVA?
You'll either need a WYE on the 480V side,
You have to have a "grounded neutral leading out" on the 480V side, going by the manual. Whatever that may mean, I am not precisely sure.
I always wonder why the choice is made to deal with transformers
Like he said, there's the 1000V DC thing, a 24000TL is maybe $600-1200 less than 3 8000TLs, so that helps pay for the xfmr (or pays for it completely) and if you are running any amount of AC wire from inverters to PCC it makes a pretty big difference in impedance losses.
If a 20000TL puts out as much or more than three 7000Tls...which they seem to do where I am- I think the higher DC voltage ends up with less losses when it's overcast often maybe.
COuld be the opposite elsewhere, but an extra MW a year is nothing to sneeze at!
I would usually spec inverters that match the service voltage.
Yes, if you can, sure, but there are sometimes "rules"... over 50kW of PV where I am *might* have to be a 3 phase service.
I can see how that makes sense- if you wanted to put in 50kW of 120V (/208 or /240V) inverters, the POCO would have to put in a 75kVA xfmr- but 75kVA also happens to be 200A of 208/120.
They might say "could you do six 8000w or 10000w inverters instead and we'll go with three phase". It is a lot better for the grid I suppose.
Then of course the customer would need a 208V to 240V buck boost or something...
I wouldn't use a 45 kVA- I'd use 3 of these, wired in Y on both sides.
http://www.temcoindustrialpower.com/products/Transformers_-_General/HT0025.html
The xfmr(s) are the only way the PV power is getting anywhere- I'd probably even use the better 25kVA model of that one above that costs $1000 more.
With 45kVA you're running the xfmr(s) at 80% much of the time- if you go with 75kVA of xfmr(s), the 40kVA of inverters will be 53.3% of the xfmr(s)- much more efficient.
If I'm reading this right, you'd have to go from 480/277V inverters thru a xfmr to 480V delta and then another xfmr, 480 delta to 208/120Y, and they'd both have to be 2x the inverter kVA.
This is for medium voltage connections, but wouldn't the step down connection have to be the same setup?
edit:whoops!
forgot the link.
http://files.sma.de/dl/7418/STP24-US_MV_Trafo-TI-en-10.pdf
You might be able to use a 45kVA- SMA says the inverter kVA has to be 90% of the xfmr size, so 40kVA plus 10% = 44kVA?
I am confused, you are not an electrician, you are not an engineer. Just what are your qualifications to give any of this advice?
Where did you get this information?
Welcome to the Internet.I am confused, you are not an electrician, you are not an engineer. Just what are your qualifications to give any of this advice?
There is no reason one would have to go through two transformers to get from 480/277 to 208/120 and no reason for the transformers' kVA rating to have to be twice the inverter's kW rating. I have done this; have you?If I'm reading this right, you'd have to go from 480/277V inverters thru a xfmr to 480V delta and then another xfmr, 480 delta to 208/120Y, and they'd both have to be 2x the inverter kVA.
Welcome to the Internet.
Welcome to the Internet.
There is no reason one would have to go through two transformers to get from 480/277 to 208/120 and no reason for the transformers' kVA rating to have to be twice the inverter's kW rating. I have done this; have you?
And ain't that what the internets are for...reading stuff?
The reality is, many manufacturers have no idea how 'electrical power systems' actually function and interact. Their instruction examples cannot possibly be able to address all of the world's electrical sources.