What it is and what it does
The Siemens 5SY4105-7 is a 1-pole miniature circuit breaker from the SENTRON family, designed for branch-circuit protection in industrial control panels. Its C tripping characteristic handles moderate inrush currents — common for motor starters, contactor coils, and small transformers — without nuisance tripping, while still clearing faults fast. Rated 10 kA breaking capacity per EN 60898 at 400 V AC, and 35 kA per IEC 60947-2, it covers most panelboard and distribution board fault levels in European 400 V networks.
Key ratings — what they mean for fit
The 10 kA rating under EN 60898 is the standard for domestic and light commercial final circuits; the 35 kA under IEC 60947-2 gives you headroom for industrial panel short-circuit capacity. At DC, it's rated 15 kA per IEC 60947-2, so it also works in DC auxiliary circuits. The 5 kA per UL 1077 means it's recognized as a supplementary protector for North American panels — not a branch-circuit breaker per UL 489, but fine for internal equipment protection. The 18 mm width (1 modular unit) snaps onto standard DIN rail. Pollution degree 3 and overvoltage category III suit fixed installations in industrial environments where conductive dust and transient surges are expected. The IP20 rating with connected conductors is typical for enclosed panel mount — no special sealing needed inside a cabinet.
Panel integration notes
Mounts in any position on 35 mm DIN rail. The quick-assembly system means it clips in without tools and the combined terminal top and bottom accept busbars or ring-tongue lugs. Installation depth is 70 mm behind the panel face, leaving clearance for wiring. The sealable design lets you lock the toggle position after commissioning to prevent unauthorized switching.