What it is and what it does
The Siemens 5SY5105-7 is a SENTRON miniature circuit breaker (MCB) — a C-curve, single-pole device rated for universal current (AC/DC) at 400 V AC / 220 V DC, with a breaking capacity of 10 kA per IEC/EN 60898-2 and 15 kA per IEC 60947-2 at DC. It occupies one modular width (18 mm) on a DIN rail, with a depth of 76 mm and an installation depth of 70 mm. The C-curve characteristic (tripping between 5× and 10× rated current) makes it a standard choice for general-purpose protection of inductive and resistive loads in distribution boards — motor starters, contactor coils, lighting circuits, and small transformer feeds.
Standards and approvals
Dual-rated to IEC/EN 60898-2 and UL1077, so it passes both European and North American acceptance criteria for supplementary protectors. Overvoltage category III, pollution degree 3 — rated for fixed-installation distribution panels where transient overvoltages are common. The housing is halogen-free and silicon-free, which matters for panels in clean-room or high-reliability environments where outgassing can contaminate contacts or optics.
Mounting and integration
Snaps onto DIN rail via the quick-assembly system; any mounting position is allowed. At 18 mm wide (1 MW), it fits standard 18 mm pitch terminal blocks and leaves room for adjacent breakers or auxiliaries. The combined terminal top and bottom accept conductors without special tools. Sealable — useful for utility-metering or tamper-proof installations. IP20 with connected conductors, so it belongs inside an enclosure, not exposed to washdown.