D-curve MCB for motor and transformer branch protection
The Siemens 5SY4625-8 is a SENTRON miniature circuit breaker with a D tripping characteristic, designed to handle the high inrush currents of motor loads, transformers, and power supplies without nuisance tripping. Its 4-pole 3P+N construction switches the neutral conductor and occupies 4 modular width units on the DIN rail — a clean 72 mm wide footprint that fits standard distribution boards. The 76 mm depth leaves clearance behind the panel door; installation depth is 70 mm. Rated for AC operation at 400 V and 50/60 Hz, with a maximum operating voltage of 440 V in multi-phase or single-phase operation. On the DC side it carries a rated voltage of 60 V, max 72 V. The D curve means magnetic trip thresholds are roughly 10–20× rated current — exactly what you need to avoid tripping on transformer inrush or motor start.
Breaking capacity — dual-standard certification
This breaker carries dual ratings: 10 kA per EN 60898-1 and 20 kA per IEC 60947-2, plus 15 kA at DC per IEC 60947-2 and 5 kA per UL 1077 / CSA C22.2 No.235. The 20 kA IEC rating means it can be applied on industrial panels with higher fault current potential — typical for main distribution boards in machine-tool or process lines. The UL 1077 listing covers North American supplementary protection applications. Certified to IEC / EN 60898-1, IEC / EN 60947-2, and UL 1077. That triple coverage lets the same part number serve panels destined for Europe (60898-1 for domestic, 60947-2 for industrial) and North America (UL 1077 supplementary) without a variant swap.
Environmental and mounting details
Rated for ambient temperatures from -40 °C to +75 °C — wide enough for unheated enclosures or machine-side cabinets. Halogen-free and silicon-free construction matters for clean-room or semiconductor-adjacent installations where outgassing is a concern. IP20 with connected conductors is standard for enclosed distribution boards; the sealable option allows the installer to lock the toggle position against unauthorized reset. Mounts in any position via the quick-assembly system. The combined terminal at top and bottom accepts both busbar and cable connections without re-termination. Pollution degree 3 and overvoltage category III suit it for fixed industrial installations where conductive dust or condensation is present.