Siemens 5SY5240-7 SENTRON — 2-Pole C-Curve MCB for Universal-Current Panels
The Siemens 5SY5240-7 is a 2-pole miniature circuit breaker from the SENTRON family, designed for universal-current operation (AC/DC) with a C-curve trip characteristic and a 10 kA breaking capacity per IEC/EN 60898-2. It also carries a UL1077 listing, making it suitable for supplementary protection in North American panels. The 2-module-width (36 mm) body snaps onto a standard DIN rail, with a 76 mm depth that clears most shallow enclosures. This is a current-production part — no lifecycle concerns for new builds or spares.
What the Ratings Mean for Your Panel
The C-curve means magnetic trip occurs at 5–10× rated current — standard for motor circuits, lighting banks, and transformer inrush where a B-curve would nuisance-trip. The 10 kA breaking capacity at 400 V AC is the maximum fault current it can safely interrupt; for DC circuits, the same 10 kA applies per EN 60898-2, while the IEC 60947-2 rating pushes to 15 kA for industrial distribution boards. Rated for 400 V AC and 440 V DC with a maximum DC operating voltage of 500 V, it covers both single-phase and multi-phase AC supplies as well as DC bus protection. The 50/60 Hz rating confirms line-frequency compatibility.
Deployment Context — Panel Integration
Snaps onto a 35 mm DIN rail via the quick-assembly system in any orientation. The 2 MW width — 36 mm — occupies two 18 mm slots; plan your rail fill accordingly. Combined terminals top and bottom accept copper conductors; strip length and torque follow standard SENTRON practice. IP20 with connected conductors means it's protected against finger contact but not washdown — install inside a closed panel. The sealable option allows locking the handle in OFF position for lockout/tagout procedures.