Fronius IG-TL 4.0 - Criteria for the Proper Selection of String Fuses; General; Effects of Using Underrated Fuses; Fuse Recommendations

42
Criteria for the Proper Selection of String Fuses
General The use of string fuses in the inverter 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.
Criteria for the
Proper Selection
of String Fuses
The following criteria must be met for each solar module string when using fuse protection:
-I
N
> 1.5 x I
SC
-I
N
< 2.0 x I
SC
-U
N
≥ 850 V DC
- Fuse dimensions: Diameter 10.3 x 35 - 38 mm
Effects of Using
Underrated Fuses
With underrated fuses, the nominal current value may be less than the short circuit current
of the solar module.
Effect:
The fuse may trip in intensive lighting conditions.
Fuse recommen-
dations
You should only use the following fuses, which have been tested by Fronius, to ensure
problem-free fuse protection:
- Cooper Bussmann PV fuses
Fronius shall not be liable for any damage or other incidents resulting from the use of other
fuses. Moreover, all warranty claims are voided.
Application ex-
ample
Example: Maximum short circuit current (I
SC
) for 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:
PV-10A10F with 10 A and nominal voltage of 1000 V DC.
I
N
Nominal current rating of the fuse
I
SC
Short circuit current for standard test conditions (STC) according to solar mod-
ule data sheet
V
N
Nominal voltage rating of the fuse
NOTE! Only select fuses suitable for a voltage of 850 V DC.