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  • #76
    Originally posted by sensij View Post

    You are using Sunpower panels? Which model? The positive grounding was only required for the designs Sunpower (and only Sunpower) produced 10 years ago or so.

    Also, for what it is worth, the problem is with *accumulation*. If the string is negative grounded, the high voltage end will degrade faster, but ultimately, they would all degrade. (See Figure 6 in the paper, showing the same degradation after 100 min of +1000 V, but after 1000 min of +100 V)
    Of course- SP had to be different from everyone else to somehow justify inflated pricing. I haven't read reports here about their equipment outperforming equipment of other manufacturers so from my point of view it was all hype. If it had merits to the tangible levels they would've patented this and would be making money now off everyone else. Somehow no one else cared.

    [moderator: bad advice and commentary deleted]
    Last edited by sensij; 10-12-2017, 08:22 PM.

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    • #77
      Originally posted by max2k View Post

      Actually- no, it's more of a guess as I haven't connected scope there. I guessed this by looking at overall topology: http://www.elp.com/articles/powergri...ar-design.html option 3. The '-' end of the string there seems to be half DC voltage below Neutral and '+' end half DC voltage above. OTOH SMA states their inverters start producing full power from 125V DC for 240V AC so they could be switching full string voltage between AC L1 & L2 when DC is less than 240V or may be they just used option 4 and put some step up converter in front of the inverting switches.
      The paper describes a European design, with a 240VAC line and a return. That is not the situation
      in North America. Here I would expect the PV voltages to move a bit depending on how good the
      filtering is and how well the lines are balanced. In Europe it appears the PV system would be
      moving with the single line polarity, something I would consider unacceptable. All sorts of effects
      could be induced at the PV side by the entirely uncontrolled stray capacity. Bruce Roe

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      • #78
        Originally posted by sensij View Post

        No. SB6000US(-10) or SB6000US-12, if you want to use SMA.

        what is different between the sb6000us and 3.0 us-40 . I know the 3.0 is transformerless

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        • #79
          I see the sb6000 has a negative or positive fuse built in. but I didn't find any info. on the 3.o

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          • #80
            Originally posted by tim a View Post
            I see the sb6000 has a negative or positive fuse built in. but I didn't find any info. on the 3.o
            The -40 is transformerless.
            CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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            • #81
              ok maybe the last question. why do some panels need a transformer and some don't?

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              • #82
                Originally posted by tim a View Post
                ok maybe the last question. why do some panels need a transformer and some don't?
                It isn't so much that they need the transformer, it is that they need to be operating at a voltage below ground potential. Ungrounded/transformerless inverters don't generally operate that way, but with a transformer, the DC+ can be connected to ground, assuring that the voltage throughout the array will be <0.

                As far as I know, it is only Sunpower's A-300 cells that exhibit this behavior, and was last in production in 2010. The Maxeon cell used in the 235 W E19 panels and newer did not require positive grounding.


                There is another thread in which it looks like you might have a microinverter option as well, although I think going with a grounded SMA or Fronius inverter is probably the easier path.

                https://www.solarpaneltalk.com/forum...icro-inverters
                Last edited by sensij; 10-13-2017, 04:23 PM.
                CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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