SMA SB 700 - Manual (Page 45)

SMA Technologie AG Rating for a line circuit breaker
Installation Guide SB700-11:SA2006 Page 45
9 Rating for a line circuit breaker
Required technical information for the inverters used:
• Maximum output current = 3.5 A
• 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 11 A.
Selecting a line circuit breaker:
• 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, 10 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 parallel with the low-voltage grid
We assume a PV system with 9 Sunny Boy 700 inverters, with three inverters
per phase.
L1
L2
L3
N
...
Betrie b Operation Erd schlu ss Earth Fault Störu ng Failure
Photovolta ik-String wech selrichter Photovo ltaic strin g inverter
SB 1100 Betr ieb Operation Erdsc hluss Earth Fault Störung Failure
Photov oltaik- Stringwech selrich ter Photov oltaic string invert er
SB 1100 Betrie b Opera tion Erd schlu ss Ear th Fault Störu ng Failure
Photo voltaik -Strin gwe chselri chter Pho tovolta ic string invert er
SB 1100 Betrie b Op eratio n Erdschluss
Earth Fault Störung
Failure
Pho tovol taik-S tringw ech selrich ter Photovol taic string inverter
SB 1100 Betrie b Ope ration Erd schlu ss Eart h Fau lt Störun g Failure
Photov oltaik -Stri ngwec hse lrichte r Pho tovol taic str ing invert er
SB 1100 Betrie b Op erat ion Erds chluss Earth Fault Störung
Failure
Pho tovol taik-S tringw ech selric hter Photovoltaic string inverter
SB 1100