#1 Sept. 6, 2013 11:45:00

AlanETM
Registered: 2013-09-05
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Voltage of panel ouput


I have Hyundai Mono crystalline panels and the spec states the voltage at Pmax to be 30.1 volts and 37.3 volts open circuit. At my inverter the voltage (Vin) can read as low as 156 for a string of six panels delivering about 7 amps and 181V drawing 1 amp. (in total there are two strings of 6 panels each)


The cable run from panel to inverter is about 14 mtr.


The voltage at the inverter does not seem to follow any linear relationship to the resistance of the cable and to me seems too low.


Is there an explanation for the above?


Alan


 





Edited AlanETM (Sept. 6, 2013 11:45:00)

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#2 Sept. 6, 2013 12:38:00

SteveRogers
Registered: 2011-12-08
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Voltage of panel ouput


Just checked the spot figures for my two arrays of 9 panels (Moser Baer MAX 220, multicrystalline) on my SMA 3600TL inverter:


239 V = 26.6 V per panel


243 V = 27.0 V per panel


It's raining heavily here so there's only about 0.5A (200W) AC being produced.  I'll check again when the sun comes out


My cable runs are shorter than yours - I think they are 4mm core.


Steve





Edited SteveRogers (Sept. 6, 2013 12:38:00)

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#3 Sept. 9, 2013 11:18:00

bhommels
Registered: 2011-10-03
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Voltage of panel ouput


Hi Alan,


The spec relates to the panel receiving the standard test irradiance of 1000W/m2. The inverter figures you quote probably were taken at a much lower irradiance.


The Current-Volts curve is highly non-linear, and probably does not scale linearily with irradiance either. Since power is current * voltage, inverters have algorithms that try to establish the optimal working point by constantly varying the operating parameters, to maximise power delivery at any time, for any irradiance.





Edited bhommels (Sept. 9, 2013 11:18:00)

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