What this MCB does — and why the D-curve matters
The Siemens 5SL6440-8CC is a 4-pole SENTRON miniature circuit breaker with a D tripping characteristic, rated 40 A at 30 °C and 400 V AC. The D-curve means it tolerates inrush currents up to 10–14 times the rated current before tripping magnetically — sized for motor, transformer, or lighting ballast loads that draw a heavy start surge. Rated frequency is 50/60 Hz, so it covers both common line supplies.
Panel fit and temperature derating
The 5SL6440-8CC occupies 4 modular width units (72 mm wide) on a DIN rail, with an installation depth of 70 mm and overall depth of 76 mm. Mounting position is any — no restrictions on orientation inside an enclosure. The 40 A rating holds at 30 °C ambient; at 40 °C it derates to 37.72 A, at 45 °C to 36.53 A, at 50 °C to 35.3 A, and at 55 °C to 34.02 A.
Compliance documentation (RoHS, REACH, UL, IEC) is standard for the SENTRON line; the 5SL6440-8CC is rated per EN 60898 for 6 kA breaking capacity and per IEC 60947-2 for industrial applications, though the 6 kA figure is the EN 60898 rating. Vibration resistance is tested to IEC 60068-2-6 at 50 m/s² from 25 to 150 Hz.