9 sizing of a circuit breaker, Sizing of a circuit breaker – SMA SB 4200TL Multi-String Installation User Manual
Page 37
SMA
Technologie AG
Sizing of a Circuit Breaker
Installation Guide
SB4200TL-13:SE2006
Page 37
9 Sizing of a Circuit Breaker
Required data of the used inverters:
• max. output current: 19 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 (4 mm²) can be used for nominal
currents up to 25.2 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.
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 4200TL with 3 inverters per
phase
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
...