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On 2/5/2011 11:30 AM, Greg Egan wrote:
<blockquote cite="mid:4D4DA546.3040808@remotepowerinc.com"
type="cite"> <font face="Arial">Fellow Scientists,<br>
<br>
I got in a discussion with a wrench the other day. He is under
the
impression that when a PV module is at short circuit current
there is
no voltage. My understanding of electricity is that if there's
no
voltage there's no current because current needs voltage in
order to
flow. I'm seeing it as a difference in potential, voltage that
is. If
there's no difference in potential I don't understand why
current would
flow. <br>
<br>
I googled it and the few links I checked out were on his side -
zero
voltage at Isc. All this is of course irrelevant to the
business of
installing PV so if you don't care I don't blame you. <br>
<br>
So I still think that if you a precise enough meter that if you
stuck
the test leads into the cables sticking out of the back of a
shorted PV
module that you'd read some small voltage that was approaching
zero.
Any explanation of why I am right or wrong in plain English (I'm
not
really a scientist) would be welcome.<br>
<br>
All the best,<br>
<br>
Greg Egan<br>
Remote Power Inc.<br>
Fairbanks, AK</font></blockquote>
<br>
Sorry for the extra response.....<br>
<br>
Greg, in short, (pun intended),<br>
<br>
A short circuit implies just that... The leads from the PV array or
module is shorted together.<br>
<br>
In a perfect short, there is NO voltage across that short, but full
current flowing through that short circuit connection.<br>
<br>
In an open circuit, there is NO current through the circuit (it's
open), and full voltage across those two wires.<br>
<br>
In-between that short and open somewhere is the max power point
delivered to the load (inverter, CC, battery, etc)<br>
<br>
The load being a partial short. (or is that a partial open ??)<br>
<br>
boB<br>
<br>
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