
SMA Technologie AG Rating for a Line Circuit Breaker
Installation Guide SB25_30-11:SE0307 Page 55
10 Rating for a Line Circuit Breaker
Required Technical Data for the Inverters Used
• Maximum output current = 12.5 A (Sunny Boy SB 2500)
15 A (Sunny Boy SB 3000)
• Maximum permissible fuse protection for the inverter = 16 A
The choice of cable together with the way it is routed, ambient temperatures and other
underlying conditions limit the maximum fuse protection for the cable.
• In our example we assume that the chosen cable (2.5 mm²) is ideally routed and
can take a nominal current of 18.9 A.
Selecting the line circuit breakers:
• The maximum possible nominal current for the cable used and the maximum
possible fuse protection for the inverter now limit the maximum possible nominal
current for the line circuit breaker.
• In our example, 16 A is possible.
However, the thermal suitability of the line circuit breaker still needs to be checked.
Example for the thermal rating for a line circuit breaker in a photovoltaic power-
generating system operated in parallel with the low voltage grid.
We assume a PV system with 9 Sunny Boy inverters, with three inverters per
phase.
L1
L2
L3
N
...
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e
tri
eb
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ation
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ilure
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