What it is and what it does
The Siemens 5SY6401-7 is a SENTRON miniature circuit breaker (MCB) with four poles, a C-tripping characteristic, and a double-rated breaking capacity: 6 kA per EN 60898-1 for general distribution and 30 kA per IEC 60947-2 for industrial feeder duty. That 30 kA rating at 400 V AC means it can interrupt high-fault-current faults in an industrial panel without upstream fuses having to clear first — a real selectivity headroom advantage when you're coordinating a main-tie-main lineup.
Mounting and panel fit
Snaps onto DIN rail via the quick-assembly system, occupies 4 modular width units (72 mm wide), and can be mounted in any position. Installation depth is 70 mm; overall depth is 76 mm. The combined top and bottom terminals accept conductors up to the standard MCB range, and the unit is sealable for panel-lockout programs.
Standards and compliance
Rated under IEC / EN 60898-1 and IEC / EN 60947-2 / UL1077, so it carries the dual certification for both residential-style distribution boards and industrial switchgear. Pollution degree 3, overvoltage category III. Halogen-free and silicon-free construction. IP20 with connected conductors — fine for enclosed panel use, not for wet-area exposure.