The Siemens SENTRON 5SY3040-6KL is a 1P+N miniature circuit breaker rated 40 A with a B tripping curve and a 4.5 kA breaking capacity per EN 60898. The neutral pole is switched — the 1P+N design opens both phase and neutral, which is required in many national wiring rules for final subcircuits. IP20 protection applies with conductors connected, so it belongs inside a distribution board or enclosure, not in a wet location.
Integration note — what fits and what does not
The 18 mm width and standard-rail mounting mean it drops directly into any DIN-rail distribution board that accepts 1 MW modules. The sealable design (padlockable toggle) allows lockout/tagout without an external kit — the toggle accepts a standard padlock hasp. Touch protection is built into the terminals, so no separate finger-safe shrouds are needed for the line and load connections.