The Siemens 5SL6040-7KL is a SENTRON miniature circuit breaker (MCB) in the compact 1-modular-width-unit (18 mm) form factor, rated 40 A at 30 °C with a C tripping characteristic and a 6 kA breaking capacity per EN 60898.
Energy limitation class 3 means it lets through less let-through energy (I²t) than class 1 or 2 breakers, which helps with downstream component coordination. Current derating is published across the operating range: 40 A at 30 °C, 38.08 A at 40 °C, 37.08 A at 45 °C, 36.05 A at 50 °C, 34.99 A at 55 °C, and 33.9 A at 60 °C. If your panel ambient runs at 50 °C, the breaker is effectively a 36 A device — size the upstream protection accordingly.
Integration notes
Snaps onto standard DIN rail; the fastening method is standard rail (EN 60715). The sealable design (padlockable toggle) allows lockout/tagout for maintenance isolation. Touch protection is built in. The supply cord can enter from any position. Vibration resistance per IEC 60068-2-6 is confirmed. Halogen-free and silicon-free construction means no corrosive off-gassing under fault — relevant for sealed enclosures or sensitive electronics sharing the panel.