480V vs 208V inverters

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beanland said:
Issues to consider:
(4) It is normal for a 600Vdc system to be used for a 208 or 240V AC connection. At 480V, a 1000Vdc system is used. For a 1500Vdc system, they often operate at 600Vac. Check the voltage rating of the array, the modules are 600Vdc rated, stick with a 208/240V inverter and skip the transformer.
(5) An autotransformer is YGyg and has a smaller core so core loss goes down. A good choice if you must use 480V inverters on a 208V service.
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FWIW, fronius 208 inverters, and even their 240 single phase ones, do 1kv strings.
 
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electrofelon said:
FWIW, fronius 208 inverters, and even their 240 single phase ones, do 1kv strings.
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I believe beanland's point was that the inverter our friend Zee has chosen might not be suitable for an old array where everything - including panels - might be wired and rated for 600V max. Seems like a valid concern. MPPT range on the Symo 480s is 500-800? Which leaves you with a voltage constraint, perhaps, of 500-600V, which strikes me as narrow.
 
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jaggedben said:
I believe beanland's point was that the inverter our friend Zee has chosen might not be suitable for an old array where everything - including panels - might be wired and rated for 600V max. Seems like a valid concern. MPPT range on the Symo 480s is 500-800? Which leaves you with a voltage constraint, perhaps, of 500-600V, which strikes me as narrow.
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Oh ok , good point. I hadn't considered that a 480 inverter might have a higher low voltage spec. I just checked it looks like the symo's isn't that much higher than their 240 inverters, 50-100 volts higher. Sunny tripower is quite a bit higher.
 
SYMO 24.0-3 480:

Operating voltage range: 200-1000V
DC startup voltage: 200V
MPP-voltage range: 500-800V

Array rated Vmp: 418.2 V (17 @ Mitsubishi 170W (24.6 Vmp rated each) per string)

Symo has a huge V range input window!
 
Based on random measurements in field I figure in real world (heat) Vmp goes down about 25% from rated Vmp.
Rate Vmp is 418.2 Vmp.
So my array might run around 300 VDC.
 
So is the deal with these inverters that they will operate below 500V but just not utilize their MPPT algorithm, or not guarantee that it will settle on the actual MPP?
 
electrofelon said:
... I do recall Mr Gunn stating that he has ran across inverters that speced a wye-wye, but I assumed that was one of those frequent cases of a manufacturer meddling in things they shouldn't care about.
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That was years ago. I suspect you are correct about the spec error; I always use wye on the inverter side and delta on the utility side now.
 
jaggedben said:
So is the deal with these inverters that they will operate below 500V but just not utilize their MPPT algorithm, or not guarantee that it will settle on the actual MPP?
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The MPPT range published on the datasheet, is the range where performance can achieve the published CEC weighted efficiency. It may operate lower than the MPPT range and still seek the array's sweetspot, but the inverter will have to activate boost converters, which hinders its efficiency. So the low input voltage limit of the MPPT range is a soft limit, not a hard one.
 
Carultch said:
The MPPT range published on the datasheet, is the range where performance can achieve the published CEC weighted efficiency. It may operate lower than the MPPT range and still seek the array's sweetspot, but the inverter will have to activate boost converters, which hinders its efficiency. So the low input voltage limit of the MPPT range is a soft limit, not a hard one.
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That rings a bell, that there are different ranges based in published efficiency - I have seen that before. But take a look at this and tell me what the difference between "rated" and " operating" mopt range is :?

https://www.powerfromsunlight.com/e...er-inverter-specifications-part-1-input-data/
 
Zee said:
Some info needed on commercial systems. I do mainly resi.

IN GENERAL
For commercial, what is the most common AC Voltage in the USA?
How common is 208 Vac Wye?
If, as I read, 208 is the most common commercial voltage why are "all" solar inverters 480V/277V?
Is it standard practice in comm. solar to install a transformer to get to your particular AC V?

SPECIFICALLY
Right now, I am tasked with re-powering an (E) 28 kW-DC, 15 yr old system with an (E) 208 V Wye Xantrex inverter (30 kVA) and separate ground mounted isolation transformer.
I am having a helluva time finding a good inverter match.

To make it harder, The DC circuit is combined on roof into a single #2/0 conductor circuit.
So, I need a single inverter (not two).
I also need a single DC input on that inverter that can handle that amperage. Many 30 kW inv.s seem to have multiple inputs.
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Three single-phase 120v invertors giving each connected to one of the three phases and neutral will work. If they do not have isolation between DC IP and AC OP the DC feeds will have to be separate and ungrounded.
You can also use 208v inverters connected between phases such as made by SolarEdge. Also each needs own isolated, ungrounded DC .
 
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electrofelon said:
That rings a bell, that there are different ranges based in published efficiency - I have seen that before. But take a look at this and tell me what the difference between "rated" and " operating" mopt range is :?

https://www.powerfromsunlight.com/e...er-inverter-specifications-part-1-input-data/
Click to expand...

Interesting how they use an example with two seemingly interchangeable terms for different datasheet entries, and then give virtually the same explanation for both of them. No elaboration on the essential difference.

In that example, "rated MPPT voltage range" is the range where it can perform and meet the published efficiency. By contrast, it can still perform its MPPT process in the "MPPT operating voltage range", but it just won't perform with its published CEC efficiency. I've asked for clarification from SMA on this exact question, and learned that this family of inverters has the same efficiency vs input voltage graph for all models. The reason they have different values for "rated MPPT voltage range", instead of a common voltage range for the whole product family, is so they could publish a higher efficiency for the higher power models.
 
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