What the ratings mean for your panel
The Siemens 5SY8450-8 is a SENTRON 4-pole miniature circuit breaker with a D tripping characteristic, rated 50 A at 45 °C and 48.95 A at 50 °C. The D-curve means it tolerates the high inrush currents typical of motor, transformer, and welding loads — the magnetic trip threshold is 10–20× In, so it won't nuisance-trip on a compressor start or a drive's DC-link precharge. The 20 kA breaking capacity per IEC 60947-2 at 440 V AC and 15 kA at 72 V DC tells you it can safely interrupt a bolted fault up to that level without cascading to upstream protective devices. For a panel feeding industrial machinery, that's the coordination headroom you need.
Integration and installation constraints
Occupies 4 modular width units (72 mm wide) on a DIN rail. Mounting position is any orientation. The fastening method is a quick-assembly system; combined terminals at both top and bottom accept the incoming and outgoing conductors. Installation depth is 70 mm, overall depth with the actuator is 76 mm. IP20 with connected conductors — standard for enclosed panel mounting, not for wet-area exposure. The neutral conductor is not switched, so this is a 4-pole breaker with three protected phases and a solid neutral bar. Sealable, halogen-free, silicon-free — relevant for clean-room or food-bev installations where outgassing or tamper evidence matters.
Lifecycle and sourcing posture
Marked as current production — no phase-out or last-time-buy notice on record. The 5SY8450-8 is a standard catalog line within the SENTRON family, suited for mechanical engineering and industry applications. Sourced and quoted to order against an RFQ through independent distribution; availability and current pricing confirmed at quote time.