What it is and what it does
The Siemens 5SY4140-7CC is a SENTRON miniature circuit breaker (MCB) — a 1-pole, 40 A device with C-curve tripping characteristic, rated to interrupt 10 kA under IEC 60898. The C-curve (tripping between 5 and 10 times rated current) is the standard choice for general-purpose branch circuits feeding motor starters, contactor coils, and mixed inductive plus resistive loads in control panels. It occupies a single 18 mm modular width on a DIN rail, quick-assembly fastening, and mounts in any position. The IP20 rating applies with connected conductors — expected for panel-mounted breakers; the enclosure provides the rest of the ingress protection.
Ratings that govern fit
The headline 40 A rating holds at 35 °C ambient. Above that, the breaker derates: 36.76 A at 40 °C, 35 A at 45 °C, 33.16 A at 50 °C, and 31.24 A at 55 °C. If the panel ambient runs hot — say inside a sealed enclosure near drives — use the 40 °C or 50 °C column, not the 35 °C figure, for your continuous-load calculation. Breaking capacity: 10 kA per IEC 60898, 5 kA per UL 1077 and CSA C22.2 No.235. If the installation requires UL listing, the 5 kA figure is the one that governs. Overvoltage category III and pollution degree 3 suit the breaker for fixed-installation distribution panels in industrial environments. Vibration resistance per IEC 60068-2-6: ±1 mm at 5 to 25 Hz, 50 m/s² at 25 to 150 Hz — enough for normal machine-mounted panels; not a concern unless the panel is on a high-vibration platform like a large press or engine test stand.
Panel integration notes
Depth 76 mm, installation depth 70 mm, height 90 mm, width 18 mm (one modular unit). The combined terminal at top and bottom accepts standard copper conductors. Sealable design allows lockout/tagout. Halogen-free and silicon-free construction — no silicone outgassing to foul contacts or optics in adjacent sensors.