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Thread: High DC-to-AC Ratios

  1. #11
    Join Date
    Oct 2009
    Location
    Austin, TX, USA
    Posts
    8,156
    Quote Originally Posted by Electric-Light View Post
    Utility AC is a sine-wave. What we call 120v means it has an RMS voltage of 120v which means a resistive load like a heating element will draw the same average power as 120v DC.

    At the very top of waveform is 170v. (1.41 times). Add some voltage for voltage drop and you see why DC input has to be at least 1.5 times the AC RMS voltage you're trying to create to draw out the arches without using a boost converter. (which is part of MPPT).

    I believe this is where 1.5x comes from.
    The DC:AC ratio has nothing to do with how much voltage you need to generate line AC voltage. An SMA inverter (see data sheet http://files.sma.de/dl/27676/SB3.0-7...DUS170619W.pdf) can make 240V AC from as little as 100V DC.

  2. #12
    Join Date
    Jun 2010
    Posts
    1,903
    I see what it is now. Never mind on what I said. he is talking about balancing out sum of rated kW of solar panel whose minute by minute kW output is weather dependent vs rated kW of inverter.(and its service factor) and possible implications of on-premise equipment limitations and possible contractual limits to allowable export.

    Not directly relevant but something I want to explore is possible productive valuable way to utilize the surplus production on-site.

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