The Siemens SENTRON 5SL6403-7CC is a 4-pole miniature circuit breaker (MCB) with a C tripping characteristic, rated 3 A and a breaking capacity of 6 kA per EN 60898 at 400 V AC.
It safely clears a short-circuit up to 6 kA without welding the contacts or cascading the fault upstream — adequate for most building distribution, but check your prospective short-circuit current (PSCC) at the panel; if it exceeds 6 kA, you need a higher-rated breaker (e.g., the 10 kA variants in the same SENTRON family). For a 3 A circuit, that's 15–30 A magnetic trip threshold — typical for small transformers, lighting contactor coils, or control-circuit feeds where the load isn't purely resistive. Verify your system earthing: this breaker is designed for AC networks at 400/440 V phase-to-phase.
Snap-on mounting to DIN rail EN 60715, any position. Depth behind the panel is 70 mm, total depth 76 mm — standard for the SENTRON 5SL series, so it clears most enclosure gland plates. IP20 with connected conductors (fingertip-safe terminals when wired); the front seal is sealable for anti-tamper applications. The 1.3 W power loss per pole at rated current (5.2 W total for 4 poles at full load) is modest — no special ventilation required in a standard distribution board, but factor it into your thermal budget if the panel is densely packed.