The Siemens SENTRON 5SL6040-6 is a 1P+N miniature circuit breaker rated 40 A at 30 °C with a B tripping characteristic and a 6 kA breaking capacity per EN 60898.
The B-curve trips between 3 and 5 times rated current — 120 A to 200 A magnetic trip — which makes it the right choice for resistive and general-purpose loads in residential and light commercial panels. At 40 A it handles a typical 9 kW single-phase load at 230 V. The 6 kA breaking capacity (per EN 60898) means it can safely interrupt a fault current up to 6 kA at the rated voltage; that covers most domestic and small commercial service entrances where the prospective short-circuit current stays under that threshold. Temperature derating is built in: at 40 °C ambient the breaker carries 38.08 A, at 50 °C it drops to 36.05 A, and at 60 °C it's 33.9 A.
Mounts on a standard 35 mm DIN rail in any position — vertical, horizontal, upside down — with a depth of 76 mm and an installation depth of 70 mm behind the panel face. The 18 mm width (one modular unit) keeps the rail fill factor tight. Sealable terminals let you lock the cover after commissioning to prevent tamper.