Fronius DC Box 60/12 - Manual (Page 36)

10
Criteria for the Proper Selection of String Fuses
Criteria for the
Proper Selec-
tion of String
Fuses The following criteria must be fulfilled for each solar module string when
using fuse protection:
-
I
N
> 1.5 x I
SC
- I
N
< 2.00 x I
SC
- V
N
>/= max. input voltage of inverter being used:
Fronius IG 15 - 60........... 530 V DC
Fronius IG Plus ............... 600 V DC
Fronius IG TL.................. 850 V DC
- Fuse dimensions: Diameter 10.3 x 35 - 38 mm
I
N
......... Nominal current rating of fuse
I
SC
....... Short circuit current for standard test conditions (STC) according
to solar module data sheet
V
N
....... Nominal voltage rating of fuse
Effects of
Using Under-
rated Fuses With underrated fuses, the nominal current rating of the fuse is less than
the short circuit current of the solar module.
Effect:
The fuse may blow under intensive irradiance conditions.
Fuse Recom-
mendations -
Application
Example NOTE! Only select fuses whose nominal voltage is higher or
equal to the max. input voltage of the inverter being used.
Example: Maximum short circuit current (I
SC
) of the solar module = 5.75 A
According to the criteria for selecting the correct fuse, the fuse must have
a nominal current greater than 1.5 times the short circuit current:
5.75 A x 1.5 = 8.625 A
The fuse that should be selected according to the „Fuses“ table: 50 215
06.10 with 10.0 A and nominal voltage 900 V AC / DC.
General The use of string fuses in the Fronius DC Box 60/12 also adds fuse
protection to the solar modules.
A crucial factor for the fuse protection of solar modules is the maximum
short circuit current I
SC
of the respective solar module.