The Siemens 5SY4163-6 is a SENTRON miniature circuit breaker rated 63 A at AC with a B-curve trip characteristic. That B-curve means it trips between 3 and 5 times rated current — standard for protecting resistive and general-purpose loads where you want fast clearing on moderate overloads but no nuisance trips from inrush. One pole, 18 mm wide, so it fits a single modular slot in any DIN-rail distribution board. Breaking capacity is 10 kA per EN 60898 and 15 kA per IEC 60947-2 at 230/400 V AC. The IEC 60947-2 rating is the one that matters for industrial panel designs — it certifies the breaker can clear a 15 kA prospective fault without welding or arcing over. Pollution degree 3 and overvoltage category III mean it's rated for fixed installations inside a control cabinet, not just residential load centers.
Thermal derating — what the 63 A actually delivers
The 63 A rating holds at 35 °C ambient. At 40 °C it derates to 59.16 A, at 50 °C to 55.06 A, and at 60 °C to 50.65 A. If your panel internal temperature runs 50 °C — common in a sealed enclosure with other heat sources — you're limited to 55 A continuous. Plan the load accordingly; the B-curve won't save you from a thermal trip on a borderline circuit.
Mounting and physical fit
18 mm wide (one modular unit), 90 mm tall, 76 mm deep. Fastens via the quick-assembly system — snaps onto DIN rail, no tools needed. Installation depth is 70 mm.
Environmental and compliance
Halogen-free and silicon-free construction — important for installations where outgassing can corrode contacts or optics. Ambient temperature range -40 °C to 75 °C, with humidity limits: 95% RH up to 55 °C, tapering to 35% at 75 °C. IP20 with connected conductors, so it's protected against finger contact but not washdown. Touch protection is built in (fingers won't reach live parts when installed in a standard distribution board).