Siemens SENTRON 5SY7632-8 — D-curve MCB for high-inrush loads
The Siemens SENTRON 5SY7632-8 is a 4-pole miniature circuit breaker with a D tripping characteristic, rated 32 A at 35 °C ambient. The D curve means it tolerates the high inrush currents typical of motor starters, transformers, and welding equipment — tripping between 10× and 20× rated current for short-circuit protection, so nuisance trips on startup are rare. It's built for industrial panels where the load isn't purely resistive. Rated breaking capacity is 15 kA per EN 60898 and 25 kA per IEC 60947-2, with a DC rating of 15 kA per IEC 60947-2. At 400 V AC, that SCCR covers most distribution boards downstream of a transformer. The 4-pole design (3P+N) includes switched neutral, so it's suited for TN-S or TN-C-S systems where the neutral needs isolation.
Thermal derating and mounting
Full 32 A rating holds at 35 °C; above that, derate progressively — 30.46 A at 40 °C, 29.66 A at 45 °C, 28.86 A at 50 °C, 28 A at 55 °C, 27.14 A at 60 °C. In a crowded enclosure with multiple breakers ganged, factor in the ambient rise. Pollution degree 3 and overvoltage category III let it live in industrial environments without extra isolation. Mounts on DIN rail via the quick assembly system; any position is permitted, which simplifies layout in tight cabinets. It occupies 4 modular width units (72 mm wide, 90 mm tall, 76 mm deep, 70 mm installation depth). IP20 with connected conductors — standard for enclosed distribution boards, not for wet washdown areas.
Where it fits
Siemens designates this for mechanical engineering and general industry — think machine tool cabinets, conveyor control panels, pump starter enclosures. The D curve and 4-pole switching make it a natural fit for three-phase motor branch circuits where the neutral is also switched. Temperature range spans -40 °C to 75 °C, so it's fine for unheated warehouses or outdoor enclosures in temperate climates.