The Siemens SENTRON 5SY4450-6KK11 is a 4-pole miniature circuit breaker (MCB) with a B tripping characteristic, rated at 50 A at 35 °C and designed for AC voltage systems. It carries a breaking capacity of 10 kA per EN 60898 and 15 kA per IEC 60947-2, meaning it can safely interrupt fault currents up to those levels in a 4P configuration. The B curve trips between 3 and 5 times rated current, making it a fit for resistive and general-purpose loads where inrush is moderate — think lighting, heater banks, or control transformers in a panel.
Derating and thermal limits
The 50 A rating holds at 35 °C ambient. Above that, the breaker derates: 48 A at 40 °C, 47 A at 45 °C, 45.95 A at 50 °C, 44.9 A at 55 °C, and 43.8 A at 60 °C. If the panel runs hot — say, a sealed enclosure with drives — size the load to the 60 °C figure, not the nameplate. The full operating range is -40 to 75 °C, so it handles cold starts in unheated plant rooms.
Mounting and panel fit
Snaps onto DIN rail via the quick-assembly fastening system, occupying 4 modular width units (72 mm wide). Installation depth is 70 mm; the overall depth including terminals is 76 mm. Mounting position is any — vertical, horizontal, upside-down — which helps when the panel layout is tight. Pollution degree 3 and overvoltage category III mean it's rated for the industrial control cabinet environment, not just clean dry indoor. IP20 with connected conductors; finger-safe terminals with touch protection are standard.