D-curve 40 A MCB for industrial and railway panels
The Siemens 5SY4440-8CC11 is a 4-pole miniature circuit breaker from the SENTRON series, rated 40 A with a D tripping characteristic. Its 10 kA breaking capacity per EN 60898 at 400 V AC means it can safely interrupt fault currents up to that level without upstream coordination issues in a standard industrial distribution board. Rated 400 V AC phase-to-phase, with a multi-phase rating of 440 V AC for four-pole operation. The 72 mm width (4 width units) fits standard 18 mm/module DIN-rail enclosures; mounting position is any, so it works in vertical or horizontal panel layouts without derating.
Terminal capacity and wiring constraints
Accepts solid and stranded conductors from 0.75 to 35 mm² — enough for the full 40 A load without pigtailing. Screw terminals with a tightening torque range of 2.5 to 3.5 N·m; combined terminal design at both top and bottom means you can feed through or loop out without separate busbar connectors. Sealable and touch-protected per the design, suitable for locked or metered enclosures where tamper evidence is required.
Ambient temperature range -40 to +70 °C operating, -40 to +75 °C storage.