The Siemens 5SY4505-8CV is a miniature circuit breaker (MCB) in the 5SY series, rated D0.5 for a 1-pole-plus-neutral configuration. Its interrupting capacity is 15 kA at 230/400 V AC, which means it can safely clear a fault current up to that level without rupturing — essential for high-fault installations like sub-distribution boards near large transformers.
Snaps onto standard DIN rail inside a panel or distribution board. The 1P+N form factor occupies one width module plus the neutral pole, so it fits a compact single-phase final sub-circuit. The D-curve (D0.5) means the magnetic trip threshold is 10–20× In, suited for loads with high inrush — think small transformers, solenoid banks, or control circuit supplies where a B-curve would nuisance-trip.
Rated 0.5 A continuous — verify the downstream cable and load don't exceed that.