Fronius DC-Freischaltbox 40/60 - Handbuch (Seite 29)

7
Criteria for selecting the right fuses
Type of fuse
protection,
depending upon
the solar
modules The type of fuse protection needed for the DC isolating box 40/60 will depend upon the
solar modules to be connected to it. The key factor here is the maximum short-circuit
current (I
SC
) of the respective solar module.
Criteria for
selecting the
right fuses When implementing fuse protection for strings of solar modules, the following criteria
must be met for each string:
-
I
N
> 1.5 x I
SC
- I
N
< 2.00 x I
SC
- U
N
>/= 600 V DC
- Fuse dimensions: ∅ 10.3 x 35 - 38 mm
I
N
................ Rated fuse amperage
I
SC
.............. Short-circuit current under standard test conditions, as stated in the data
specification sheet for the solar modules (STC)
U
N
.............. Rated fuse voltage
Consequences of
inadequately
dimensioned
fuses If the fuses are inadequately dimensioned (i.e. too small a rating), the rated fuse
amperage is smaller than the short-circuit current of the solar module.
Consequence:
In conditions of intense sunlight, the fuse may trip.
Recommended
fuses Fronius recommend using Littelfuse fuses. Each fuse must be dimensioned in
accordance with the “Criteria for selecting the right fuses”.
NOTE!
Only select fuses, which are suitable for a voltage of 600 V DC!
e.g.: maximum short-circuit current (I
SC
) of the solar module = 5.75 A
As specified in the “Criteria for selecting the right fuses”, the rated fuse amperage must
be bigger than a multiple of 1.5 times the short-circuit current:
5.75 A x 1.5 = 8.625 A
Fuse to be selected: KLK D 9 with 9.0 A and 600 V AC / DC
Rated amperage Fuse
1.0 A KLK D 1
1.5 A KLK D 1 1 /
2
2.0 A KLK D 2
2.5 A KLK D 2 1 /
2
3.0 A KLK D 3
3.5 A KLK D 3 1 /
2
4.0 A KLK D 4
5.0 A KLK D 5
Rated amperage Fuse
6.0 A KLK D 6
7.0 A KLK D 7
8.0 A KLK D 8
9.0 A KLK D 9
10.0 A KLK D 10
12.0 A KLK D 12
15.0 A KLK D 15
20.0 A KLK D 20