The Siemens 5SL6603-7 is a SENTRON miniature circuit breaker (MCB) rated 3 A with a C-curve trip characteristic, 4-pole (3P+N) construction, and a 6 kA breaking capacity per EN 60898 at 400 V AC. The C-curve means it holds through 5–10× rated current momentarily — enough for a motor starting or a capacitor bank charging — then clears fast. At 3 A, that's 15–30 A magnetic trip threshold.
Temperature derating — the real-world current
At 30 °C ambient, the 5SL6603-7 carries its full 3 A. But in a warm panel — say 40 °C — it derates to 2.85 A; at 45 °C it's 2.79 A; at 55 °C it drops to 2.62 A. That's not a bug, it's thermal protection physics: the bimetal strip heats faster in a hot enclosure, so the breaker trips earlier. If your panel runs warm, size up one amp rating to keep the circuit alive at full load.
Mounting position is any — upright, sideways, upside-down — the trip curve doesn't care. IP20 with conductors connected, so it's for enclosed distribution boards only, not wet environments. Pollution degree 2, overvoltage category III — standard for fixed-installation final circuits.