SMA SB 4200TL HC Multi-String - Manual (Page 51)

SMA Technologie AG Rating for a Line Circuit Breaker
Installation Guide SBTLHCMS-IEN080411 Page51
11 Rating for a Line Circuit Breaker
Required technical information for the inverters used
• Maximum permissible fuse protection for the inverter = 25 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 (6 mm²) is ideally routed and
can take a nominal current of 32.2 A.
Selecting a line circuit breaker:
• The maximum possible nominal current for the cable used and the maximum pos-
sible fuse protection for the inverter now limit the maximum possible nominal cur-
rent for the line circuit breaker.
• In our example, 25 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 electrical
power unit operated in grid-parallel mode.
A PV system with 9 inverters type Sunny Boy SB 4200TL HC Multi-String or Sunny
Boy SB 5000TL HC Multi-String is assumed, with 3 inverters per phase.
• Maximum output current = 19 A (Sunny Boy SB 4200TL HC Multi-String)
22 A (Sunny Boy SB 5000TL HC Multi-String)