Siemens 5SL4450-8 SENTRON 4-Pole MCB, D Curve, 50 A
The Siemens 5SL4450-8 is a 4-pole miniature circuit breaker from the SENTRON family, with a D tripping characteristic rated at 50 A and 400 V AC. It delivers a 10 kA breaking capacity per both EN 60898 and IEC 60947-2, covering residential and infrastructure branch-circuit protection. The D curve suits loads with high inrush — motor starters, transformers, or welding equipment — where the magnetic trip holds off until roughly 10–20× rated current.
Ratings and Derating
At 30 °C ambient the breaker carries the full 50 A; at 40 °C it derates to 47.36 A, at 45 °C to 46 A, and at 55 °C to 43.09 A. The 3.6 W power loss per pole in hot operating state adds up — in a sealed enclosure with multiple breakers, that heat must be factored into the thermal budget. The mechanical service life is rated at 10,000 switching cycles typical.
Mounting and Integration
Occupies 4 modular width units (72 mm wide) on a DIN rail; installation depth is 70 mm, overall depth 76 mm. Mounting position is any, and the enclosure is sealable. IP20 with connected conductors — standard for panelboard use, not for wet areas. Degree of pollution 2, overvoltage category III. Accepts supplementary devices (auxiliary contacts, shunt trips, undervoltage releases) for remote signaling or emergency-off circuits.