PV inverter configurator | JOTUNHEIM ENGINEERING

Your inverter

Pick an inverter from the list, or enter your own if it is not there. The values in the list are taken from manufacturers' datasheets and republished as they stand: each entry carries the revision of the datasheet it came from, and flags the ones the manufacturer still marks preliminary.

Where the values come from Inverter

Rated AC power kVA It is what sets the DC/AC ratio Maximum input voltage V Bottom of MPPT window V Top of MPPT window V Start-up voltage V Maximum current per MPPT A Maximum current per DC input A 0 if the datasheet does not give it Inputs per MPPT Number of MPPTs

Your module

The module sets the string length and the current each MPPT sees. Changing power bin changes how many modules fit, and therefore the DC/AC ratio.

Series Power bin

Your site

The lowest air temperature expected sets the maximum string length; the highest, together with the mounting, sets the minimum.

Minimum air temperature °C No thermal model: IEC 62548, NEC 690.7 Maximum air temperature °C Mounting Uc = 20 W/m²K

Filling the inverter

The two sliders give the number of strings connected. The DC/AC ratio follows, and the scale shows where it falls against the two thresholds. Each slider stops where the equipment stops, and the page says which part.

Strings per MPPT 2 MPPTs used 10

Modules connected— Array power— peak, STC conditions DC/AC ratio —

The conventions behind the calculation

They are written here because a result without its conventions means nothing. On a study, each one is taken again from your site and your equipment.

String length — the smaller of the two limits: Voc × number of modules at the coldest, below the input voltage, and Vmp × number of modules below the top of the MPPT window. It is the module comparator's calculation, taken as it stands.
Strings per MPPT — the smaller of the two: maximum MPPT current divided by Imp, or the number of inputs. No safety factor is applied.
DC/AC ratio — the array's peak power divided by the inverter's rated AC power. Up to 1.30 we consider it recommended; beyond that, clipping losses can become high; beyond 1.40, a larger inverter is preferable. Both thresholds are a JOTUNHEIM decision, and hold whatever the site.
What PVsyst actually says. PVsyst publishes an overload loss criterion: a warning from 0.2 %, a block beyond 3 %. The figures 1.25 to 1.30 so often quoted are an observed consequence of it in Europe on a well-oriented plane, not a recommendation from the software.
Clipping, what actually happens. When the array exceeds the inverter's power, the inverter holds its rated output by moving the operating point along the I/V curve. Nothing overheats, nothing ages: only the energy above the ceiling is not produced.
Cold: no thermal model — the cell is at air temperature. Hot: the PVsyst model, Tc = Ta + G·α(1−η)/Uc.

What this configurator is not

It does not calculate the clipping loss. It is derived from an annual power histogram at hourly resolution, which only a simulation produces. The page gives a ratio and a verdict, never a loss percentage — and beyond 1.30 it points to a PVsyst simulation rather than putting a figure forward.
It does not rank inverters and recommends none. It applies arithmetic to the values you enter.
It says nothing about the AC connection: transformer, protections, cable length and voltage drop are calculated elsewhere.
It ignores shading and the actual layout. Strings that pass electrically still have to fit on the roof.
Inverter values, whether chosen from the list or entered, are republished as they stand. Each entry in the list carries the revision of the datasheet it came from and the date it was recorded; two of them are marked preliminary by their manufacturer, and the page says so. We do not redistribute the datasheets: ask your supplier for them, and check the values there before committing to anything.

You are a developer, EPC or installer, and you have to decide how many strings to connect to your inverter.