RFI's Solar Product Manager Alkyra Hutchison-Menzer explains the new clause added to AS/NZS5033:2021 relating to solar string ratings versus inverter input current ratings.
Clause 4.5.1 was added to AS/NZS5033:2021 and has caused some confusion regarding the 'compatibility' of solar modules and string inverters.
This new clause ties the inverter's PV input current rating to the calculated PV string/circuit current, referencing the method outlined in Clause 4.2.2.
The simplest version of the current calculation in Clause 4.2.2 applies a x1.25 multiplier to the PV module's Isc value. Circuits with parallel strings, multiple sub-arrays and/or overcurrent protection use different calculations.
So the inverter's maximum current input rating needs to exceed this calculated 'string Isc' value (not simply the PV module's specified Isc rating on its own).
E.g. A 370W solar module has a specified Isc of 11.49A (STP370S-B60/Wnhm).
Applying the x1.25 multiplier results in a ‘string Isc’ of 14.36A.
So this module may be used with inverters which have an input current window higher than 14.36A.
When used with 5kW inverters, this can include SMA SunnyBoy 5.0-1AV-41 (20A), Sunways STS-5KTL (15A), Growatt MIN5000TL-X (16A) and APsystems DS3-S microinverter (16A).
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