What it is and what it does
The Siemens SENTRON 5SY4320-7CC11 is a 3-pole miniature circuit breaker with C-curve tripping characteristic, rated 10 kA breaking capacity per EN 60898 at 400 V AC. That C-curve means it trips between 5 and 10 times rated current — standard for protecting general-purpose industrial loads like motor feeders, control transformers, and lighting circuits where inrush isn't extreme. The 10 kA SCCR at 400 V tells you it can safely interrupt a fault up to that level without upstream damage, which is the usual requirement for distribution panels in industrial and railway applications.
Where it fits
Snaps onto DIN rail via the quick assembly system — 3 modular width units (54 mm wide), any mounting position. Installation depth is 70 mm; overall depth 76 mm. The combined terminal top and bottom accept conductors without needing separate busbar adapters for most panel layouts. Pollution degree 3 and overvoltage category III suit it for fixed installations inside enclosures where conductive dust or condensation might be present. IP20 with connected conductors — fine inside a cabinet, not for wet areas.
Key ratings and what they mean for your panel
Rated 400 V AC (multi-phase) and 440 V AC single-phase — covers most industrial supply voltages up to 480Y/277 V systems. DC rating max 72 V, so it's usable on some DC control circuits but not for higher-voltage DC bus work. Frequency 50/60 Hz. Power loss 1.7 W per pole at rated current in hot state — factor that into enclosure thermal calculations if you're packing several breakers side by side. Vibration resistance per IEC 60068-2-6: ±1 mm at 5–25 Hz, 50 m/s² at 25–150 Hz — railway and mobile equipment approved. Temperature range -40 to 75 °C ambient, with humidity derating above 55 °C. Sealable, halogen-free, silicon-free — relevant for clean-room or low-outgassing specs.