Siemens 5SY7105-7 — 0.5 A C-Curve MCB for Control and Lighting Circuits
It carries a 15 kA breaking capacity per EN 60898-1 and a 50 kA rating per IEC 60947-2 / UL1077, meaning it can safely interrupt fault currents up to those levels without upstream cascading — critical for selectivity coordination in a distribution board.
The 0.5 A rated current at 35 °C derates to 0.47 A at 40 °C and 0.4 A at 60 °C (–). If your enclosure runs warm — say, next to a transformer or drive — size the load below the derated figure, not the 35 °C number. The C-curve trips magnetically at 5–10× In, so it's suited for moderate inrush loads like contactor coils or small transformers, not pure resistive heaters (use B-curve) or heavy motor starts (use D-curve). The dual breaking capacity — 15 kA per EN 60898 and 50 kA per IEC 60947-2 — reflects the same hardware tested to two standards. The 50 kA figure applies when the breaker is used as a distribution circuit breaker per 60947-2; the 15 kA figure applies when used as a domestic/industrial MCB per 60898. For industrial panels, treat the 50 kA as your SCCR headroom, but verify the upstream fuse or breaker limits the prospective fault current to that value.
Mounting position is any; installation depth is 70 mm. Sealable allows lockout/tagout compliance.