The Siemens 5SL3303-7 is a SENTRON 5SL miniature circuit breaker (MCB) — a 3-pole unit with a C-curve tripping characteristic, rated 3 A at 400 V AC.
In a panel with elevated internal temperature, derate per the manufacturer's curve — the surrounding temperature spec allows periodic +55 °C at 95 % humidity, so the breaker is built for warm enclosures, but the trip threshold shifts. The 4.5 kA SCCR at 400 V AC means it safely interrupts faults up to that level without welding or cascading upstream — coordination with a higher-rated upstream device is required if the prospective fault current exceeds 4.5 kA. The 3-pole design switches all three phases simultaneously, which is critical for three-phase loads where a single-phase trip could backfeed and create a shock hazard. Rated voltage is 400 V AC for multi-phase operation, with a maximum of 440 V AC. The DC rating is 72 V maximum — this is not a DC-rated breaker for solar or battery strings above that voltage. The energy limiting class is 3, meaning it limits let-through energy well, reducing arc-flash risk downstream.
Snap-on DIN rail mount, 3 module widths (54 mm). Sealable with a lockable cover or clip, which matters for LOTO compliance on a circuit that must be positively isolated. Halogen-free and silicon-free construction for environments sensitive to outgassing (clean rooms, medical, data centers).