String Sizing Tool producing bizarre VOC temperature values

[openplanet]

Hello--

Please take a look at the attached PDF of a String Sizing Tool output.  The VOC temperatures under Design Check make no sense to me.  Can anyone explain? 

--Thank you

[Vic]

Hi o p,

To me,  all that the Design Check is saying,   is that strings of four of those PVs,   the Classic 150 is always in HyperVoc,   and will probably be damaged.  The Classic 200 enters HyperVoc at 56.6 F  (not so useful),   but the Classic 250  will not enter HyperVoc until the array temp reaches almost -90F.

As you know,  HyperVoc is the point where the Classic will cease producing power,   and Rests,   trying to protect itself.

Make sense?  Vic

[openplanet]

Somehow those numbers just don't make sense.  The difference, for example between when the 200 and 250 enter HyperVOC seems absurdly huge.  Is there possibly a problem with the tool?

[FNG]

4 modules at 48 volts = 192 volts

To adjust for temperature you have .33 % per degree C

53.6F is 12C
-88.6F is -67C

So now lets do the math on the 200, 25C neutral point to 12C is 13 degrees
.33% x 192 volts is .63v x 13 degrees delta is 8.2 volts, Add 8.2v to 192 and you have 200.8V so the Classic 200 is in hyper voc


So now lets do the math on the 250, 25C neutral point to -67C is 92 degrees
.33% x 192 volts is .63v x 92 degrees delta is 57.96 volts, Add 57.96v to 192 and you have 250V so the Classic 250 is in hyper voc