What it is and what the ratings mean
The Siemens 5SL4540-7CC is a 1+N-pole miniature circuit breaker rated 40 A at 230 V with a 10 kA breaking capacity, C-curve trip characteristic. The C-curve means it trips at 5 to 10 times rated current — suited for inductive loads like small motors, lighting ballasts, and transformer primaries where a moderate inrush is expected without nuisance tripping. The 10 kA breaking capacity at 230 V tells you it can safely interrupt a fault current up to that level, which is the standard for most residential and light commercial distribution boards in Europe and markets following IEC 60898. The 1+N-pole configuration switches the phase and provides a switched neutral, common in single-phase final circuits where isolating both conductors is required for maintenance safety.
Panel integration notes
As a DIN-rail mount device in the 5SL series, it snaps onto a standard 35 mm DIN rail per EN 60715. The 1+N-pole width occupies two modular spaces (36 mm). Terminal capacity accepts up to 25 mm² conductor for the incoming supply and outgoing load — sized for the 40 A rating without needing a ferrule or bootlace. The C-curve characteristic means coordination with upstream and downstream devices should follow the manufacturer's selectivity tables; at 40 A and 10 kA, this breaker coordinates well with a 63 A or 80 A upstream SENTRON NH fuse or a higher-rated 5SL series MCB for full discrimination up to the fault level.