9 sizing of a circuit breaker, Sizing of a circuit breaker – SMA SB 5000TL Multi-String Installation User Manual
Page 37
SMA
Technologie AG
Sizing of a Circuit Breaker
Installation Guide
SB5000TL-12:SE2006
Page 37
9 Sizing of a Circuit Breaker
Required data of the used inverters:
• max. output current: 22 A
• max. permissible rating of the circuit breaker for one inverter: 25 A
The type of cable as well as the type of cable installation and several other conditions
have influence on the maximum rating of the circuit breaker for the inverter.
• In this example we assume that the cable used (6 mm²) can be used for nominal
currents up to 32.2 A in this example.
Selection of the circuit breakers:
• The maximum possible nominal current of the cable used and the maximum pos-
sible rating for the inverter now define the maximum possible nominal current of
the circuit breakers.
• 25 A are possible in our example for one inverter.
The circuit breakers must also be selected according to their thermal characteristics.
Several aspects that have affect on the load must be considered when you select a
circuit breaker. These aspects are specified in the data sheets of the circuit breakers.
Example for the sizing of a circuit breaker for the AC line of a photovoltaic in-
verter for utility interaction in terms of temperature.
Photovoltaic plant with 9 inverters type Sunny Boy 5000TL Multi-String with 3
inverters per phase
Example for the sizing of a 25 A circuit breaker with B characteristics for the
AC line of a photovoltaic inverter for utility interaction while the circuit break-
ers are installed right next to each other without gap (with respect to the ther-
mal conditions).
L1
L2
L3
N
A
rt
.-N
r.:
8
6
-0
0
A
rt
.-N
r.:
8
6
-0
0
A
rt
.-N
r.:
8
6
-0
0
A
rt
.-N
r.:
8
6
-0
0
A
rt
.-N
r.:
8
6
-0
0
A
rt
.-N
r.:
8
6
-0
0
...