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480V vs 208V inverters

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  • electrofelon
    replied
    Originally posted by Carultch View Post
    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.
    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/ea...-1-input-data/

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  • Carultch
    replied
    Originally posted by jaggedben View Post
    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?
    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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  • ggunn
    replied
    Originally posted by electrofelon View Post
    ... 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.
    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.

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  • jaggedben
    replied
    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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  • electrofelon
    replied
    Originally posted by Zee View Post
    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 isn't that below the inverters mppt window?

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  • Zee
    replied
    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.

    Leave a comment:


  • Zee
    replied
    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!

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  • electrofelon
    replied
    Originally posted by jaggedben View Post
    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.
    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.

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  • jaggedben
    replied
    Originally posted by electrofelon View Post
    FWIW, fronius 208 inverters, and even their 240 single phase ones, do 1kv strings.
    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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  • electrofelon
    replied
    Originally posted by beanland View Post
    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.
    FWIW, fronius 208 inverters, and even their 240 single phase ones, do 1kv strings.

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  • electrofelon
    replied
    Originally posted by jaggedben View Post
    I'm no expert on transformer engineering but I don't understand how the utility side configuration has any effect on this.
    Same here. I am open to being schooled in this. Inverter could still detect utility L-G voltages as the utility ground/neutral will be solidly connected to the inverter side neutral thru the egc system, so I am skeptical. Also not sure why "some" inverters would want that and others wouldn't. 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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  • jaggedben
    replied
    Originally posted by beanland View Post
    Issues to consider:
    (1) If the inverter needs to properly sense line-ground voltage to properly implement anti-islanding, you will need to use a YGyg transformer. If you use a Dyg transformer, you lose the ability to properly sense line-ground voltages.
    ...
    I'm no expert on transformer engineering but I don't understand how the utility side configuration has any effect on this.

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  • beanland
    replied
    YGyg vs. Dyg

    Issues to consider:
    (1) If the inverter needs to properly sense line-ground voltage to properly implement anti-islanding, you will need to use a YGyg transformer. If you use a Dyg transformer, you lose the ability to properly sense line-ground voltages.
    (2) Transformers can move power in both directions but are often rated for excitation and energization from one side. That would be the utility side. The concern is how close the windings are to the core and the resulting inrush current. Consult the manufacturer.
    (3) A transformer introduces 24x7 no-load loss and operational I2R loss. Both impact the overall PV system performance. Consider those when selecting a transformer.
    (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, if 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.

    Leave a comment:


  • electrofelon
    replied
    Originally posted by ggunn View Post
    Some (most?) transformers are listed for bidirectional operation but some are not; that's a question for the manufacturer. You'll want your transformer to be delta (no neutral) on the utility side and wye (grounded neutral, separately derived) on the inverter side.
    And just to clarify, I believe that a transformer must be listed/marked as suitable for being "reverse fed" and applies to which side supplies the magnetizing current, not which way the energy (usually) flows. In other words a transformer used for a pv system need not be marked as suitable for reverse feed.

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  • ggunn
    replied
    Originally posted by Zee View Post
    Thank you, both.

    Yes, I am told I need a neutral.

    The building does have a 208Y/120 3PH 4W system.

    Curious in general with transformer terminology:
    I noticed you specified a "step up transformer" and you also mention "208V to 480V" and not the other way around (480V to 208V)? I just want to be 100% sure these two indicate line and load and it is fixed.
    In other words: solar must be on the load side in general and the utility on the line side?

    Silly me, from a theoretical perspective, I always thought transformers would work in either direction.......of course with opposite effect. But it seems the line and load sides are fixed also?
    Just theory, but good to know.
    Some (most?) transformers are listed for bidirectional operation but some are not; that's a question for the manufacturer. You'll want your transformer to be delta (no neutral) on the utility side and wye (grounded neutral, separately derived) on the inverter side.

    Leave a comment:

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