The Siemens 5SJ6306-7 is a SENTRON 5SJ6 miniature circuit breaker — 3-pole, C-curve, rated 6 A at 400 V AC, with a 6 kA breaking capacity per EN 60898 and IEC 60947-2. On a 3-pole 400 V line, that 6 kA SCCR handles most distribution panel fault levels without cascading upstream.
On a 3-phase 400 V supply, that works out to roughly 4 kW of resistive load or a 3 kW motor with C-curve headroom. The C-curve (5–10× In) gives you enough inrush margin for small motors, contactor coils, and lighting ballasts without tripping on start-up. At DC, the maximum rated voltage is 60 V — so this breaker can also serve a 48 V or 24 V DC control bus, but not a 125 V DC railway or solar string. The 50 Hz rating is the standard mains frequency; it will operate at 60 Hz without issue, but the thermal-magnetic trip curve is calibrated for 50 Hz. The temperature range is -40 to 75 °C, which covers unheated enclosures in cold climates and hot panel interiors near transformers.