Trace ST problems [RE-wrenches]

[Bill Brooks]

The Sun-Tie was specifically designed for the EPV specs.

I'm also not sure why the high frequency nature of the inverter would make a
difference. I may not understand their circuitry exactly, but most high
frequency inverters have a very real lower voltage boundry that is directly
tied to line voltage. I would be surprised if the Sun-Tie was dramatically
different.

Bill.


-----Original Message-----
From: Eric Smiley [mailto:Eric_Smiley at bcit.ca]
Sent: Tuesday, March 06, 2001 1:39 PM
To: RE-wrenches at topica.com
Subject: RE: Trace ST problems [RE-wrenches]






>Remember that EPV modules have a very poor fill factor and therefore
are not
>far off the max power point with a few volts. However, I have seen EPV
>modules operating at much lower than 39 Volts (try 34 Volts). A good
rule of
>thumb is to not believe manufacturers specifications--that goes for
modules
>and inverters.

I have witnessed the same thing with EPV modules. However, I spoke with
Tobin Booth at Trace and he confirmed my suspicion that the 42 - 85 V
MPPT window is conservative. (Also one would assume EPV would carefully
select modules for a demo system)
Personally, I still wouldn't spec EPV modules with a SunTie, but I'm no
longer so concerned about pairing other a-Si modules with the ST.

>The MPPT window of an inverter is based on the line voltage. The low
end of
>the voltage range is always suspect from the manufacturer. If the line
>voltage is 124Volts (3%high) the low end of the MPPT window just went
up 3%
>(that would be about 44 Volts on the Sun-Tie). Now we have a 10 Volt
>differential--Very significant power loss.
I think this would be true for a low frequency inverter. However, since
the ST has a high frequency topology, it probably isn't strictly a
linear relationship.



      ----------------------------------------------------------------------

      Eric Smiley
      Project Leader - BCIT Technology Centre
      Photovoltaic Energy Applied Research Lab (PEARL) - BCIT
      ph: (604)432-8657 www.bcit.ca/~tc/pearl/index.htm

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