The Siemens 5SN6640-7CN is a SENTRON miniature circuit breaker rated 40 A with a C-curve trip characteristic, 3P+N four-pole design, and a 6 kA breaking capacity at 400 V AC per EN 60898. It occupies 4 modular width units (72 mm) on a DIN rail — a standard 4-pole footprint that fits most residential and light-commercial distribution boards. The C-curve means it trips between 5 and 10 times rated current, sized for general-purpose loads like lighting, socket circuits, and small motor starters where inrush isn't extreme.
Panel fit and wiring
Mounts in any position on a 35 mm DIN rail; installation depth is 70 mm, overall depth 76 mm. The 4-module width (72 mm) matches the standard 4-pole MCB slot — no surprises swapping into a panel laid out for SENTRON or comparable DIN-rail breakers. Solid conductors up to 25 mm² fit the terminals, which covers most 40 A feed circuits. The IP20 rating applies with conductors connected, so it's fine inside a closed enclosure but not for wet or dusty environments. Touch protection is built in, and the neutral pole is switched (3P+N). Power loss is 3.3 W per pole in hot operating state at rated current — about 13.2 W total for all four poles. That's moderate for a 40 A breaker; check your enclosure's thermal derating if packing several breakers side by side. Vibration resistance is 50 m/s² at 25 to 150 Hz per IEC 60068-2-6, which is standard for panel-mounted switchgear.
Rated for overvoltage category III and pollution degree 2 — standard for fixed-installation distribution boards. The operating temperature range is -40 °C to +75 °C, with periodic humidity up to +55 °C and 95% RH. Halogen-free and silicon-free construction, sealable for tamper-proofing. Supplementary devices can be installed (auxiliary contacts, shunt trips, alarm switches) via the accessory slots. Frequency rating is 50/60 Hz; maximum operating voltage is 440 V AC multi-phase.