The 5SP3350-3 is a 3-pole main miniature circuit breaker from the Siemens SENTRON family, rated 400 V AC at 50 Hz with a 25 kA breaking capacity per EN 60898. This makes it a fit for main feeders where you need discrimination downstream.
At 4.5 modular width units (roughly 81 mm), it occupies a bit more than a standard 3-pole MCB — plan panel space accordingly. The integrated locking slide accepts a padlock, wire seal, or cable tie, so it can be locked in the OFF position for LOTO procedures. Saddle terminals are standard; no need for pin ferrules on stranded conductors. Rated IP40 with conductors connected, so it's suited for enclosed distribution boards.
Shock resistance tested at 30 g, 11 ms half-sine, 3 impacts per axis; vibration tested per IEC 60068-2-6 at 2 g, 5–150 Hz sweep. That's enough for transport and installation in commercial buildings, less so for direct mounting on heavy machinery — but in a distribution board, it holds. Mechanical service life is 20,000 operating cycles typical — more than enough for a main breaker that cycles maybe a few times a year.