by David Wren
Because the characteristics of PV Array modules vary with temperature, this will result in the operation of the gPV fuse links being reduced as the ambient temperature increases.
As illustrated in the typical characteristics below.
As the ambient temperature exceeds 30°C degrees, the ‘Percentage of Rated Current’ of the fuse links tails off. Until at 80°C, it has dropped to about 77% of it’s normal characteristics.
To enable the design engineer to take higher ambient temperature conditions into consideration, when designing the distribution for a PV Array, Derate data fields have been added to the CPD DB program. This new function will allow engineers to enter the manufacturers’ Temperature Derating data for gPV fuses.
In the PV Solar Sizing dialog, on the tab for the AC/Inverter, there is a new data field Enclosure Temp.
When a higher worst-case temperature is selected for the installation location of the PV Array (which will result in reduced fuse performance), the Derate data is used in the calculations to check if a fixed fuse rating is of the appropriate size.
In the example above, the selected Enclosure Temperature is 65°C. In the previous image of the Derate data for the 15A to 20A gPV fuses, the factor for 65°C is 0.87. Therefore, if a 20A rated gPV fuse was used for the PV Array or the Array’s Strings at 65°C, the effective rating of this fuse would be reduced to 17.4A. (20A x 0.87).