SolarEdge Inverter with P860 Voltage Drop Calculation

[Cudal81]

Hi I'm confuse on the voltage drop calculation to what number will I use for the operating current (I) and circuit voltage (Vcircuit)

am I right for this system?
I = 18A
Vcircuit = 400Vdc

Thank you

 

[Carultch]

Hi I'm confuse on the voltage drop calculation to what number will I use for the operating current (I) and circuit voltage (Vcircuit)

am I right for this system?
I = 18A
Vcircuit = 400Vdc

Thank you

You can use 18A as a worst-case scenario, but it is conservative to do so. A more realistic value will come when you account for the current that corresponds to the power per string, and the typical operating voltage. The inverter input is also limited, in this case to 38A of usable current for each of the three power stages. The inverter will push up the DC voltage within the window between 400V and 600V, when the current approaches this limit, so it is rare that you'll operate the strings at the full 18A.

SolarEdge has a white paper called "labeling your SolarEdge system", which applied for code cycles where you were required to label all four Amp and Volt figures at every DC disconnect. This white paper describes how the voltage and current numbers relate to Voc, Isc, Vmp and Imp, as you are accustomed to calculating with ordinary arrays. From that white paper, it provides the following equivalencies.
Equivalent to Voc, is the maximum DC voltage governed by the inverter, in this case 600V.
Equivalent to Vmp, is to the typical operating DC voltage governed by the inverter, in this case 400V.
Equivalent to Isc, is the maximum current of the optimizers, in this case 18A.
Equivalent to Imp, is calculated from P=I*V, solved for I. Plug in typical operating voltage for V, and the total STC power per string.

In an ordinary system, you use Vmp and Imp to calculate voltage drop. In an optimizer system, you use the equivalent values to Vmp and Imp, as I described above.

 

[Cudal81]

You can use 18A as a worst-case scenario, but it is conservative to do so. A more realistic value will come when you account for the current that corresponds to the power per string, and the typical operating voltage. The inverter input is also limited, in this case to 38A of usable current for each of the three power stages. The inverter will push up the DC voltage within the window between 400V and 600V, when the current approaches this limit, so it is rare that you'll operate the strings at the full 18A.

SolarEdge has a white paper called "labeling your SolarEdge system", which applied for code cycles where you were required to label all four Amp and Volt figures at every DC disconnect. This white paper describes how the voltage and current numbers relate to Voc, Isc, Vmp and Imp, as you are accustomed to calculating with ordinary arrays. From that white paper, it provides the following equivalencies.
Equivalent to Voc, is the maximum DC voltage governed by the inverter, in this case 600V.
Equivalent to Vmp, is to the typical operating DC voltage governed by the inverter, in this case 400V.
Equivalent to Isc, is the maximum current of the optimizers, in this case 18A.
Equivalent to Imp, is calculated from P=I*V, solved for I. Plug in typical operating voltage for V, and the total STC power per string.

In an ordinary system, you use Vmp and Imp to calculate voltage drop. In an optimizer system, you use the equivalent values to Vmp and Imp, as I described above.

followup question since I'm using P860 optimizer where I can connect 2 modules per optimizer would I compute the power as
(STC power rating per module) x (no of module)
or
(STC power rating per module) x (no of optimizer)
thank you

 

[jaggedben]

Number of modules.

 

[Cudal81]

Number of modules.

thanks jaggedben