What it is and what it does
The Siemens 5SY5140-7CC is a 1-pole miniature circuit breaker from the SENTRON family, designed for DC branch-circuit protection. Its C-curve tripping characteristic means it handles moderate inrush currents — typical for motor starters, contactor coils, and control transformers — without nuisance trips, while still clearing overloads and short circuits. Rated 40 A at 35 °C and 37.28 A at 40 °C, it's sized for a 40 A DC load at a 35 °C ambient; above that, the thermal derating is already on the nameplate. The DC breaking capacity is 10 kA per IEC 60947-2, which covers most industrial 220 V DC bus faults. Pollution degree 3 and overvoltage category III place it in fixed industrial panels where conductive dust and switching transients are normal.
Panel fit and mounting
Width is 18 mm — one modular unit on a standard DIN rail. Depth is 76 mm, with an installation depth of 70 mm. The quick-assembly fastening method clips onto the rail without tools; mounting position is any orientation. Combined terminals top and bottom accept both busbar and wire connections. IP20 with connected conductors means it's protected against finger contact but not washdown — standard for enclosed panelboards. Halogen-free and silicon-free construction matters for clean-room or high-reliability environments where outgassing can contaminate contacts or optics.