What this MCB is and where it fits
The Siemens 5SY6425-7 is a SENTRON miniature circuit breaker (MCB) with four poles, a C-trip curve, and a rated breaking capacity of 6 kA per IEC/EN 60898-1 or 15 kA per IEC/EN 60947-2. It's built for 400 V AC distribution panels in mechanical engineering and industrial environments, where the C-curve handles moderate inrush from motor starters and transformer banks without nuisance tripping. Rated 6 kA under the domestic-standard EN 60898-1 and 15 kA under the industrial-standard IEC 60947-2 — the higher figure governs panel SCCR coordination when the breaker is part of a listed industrial assembly. The same 15 kA rating applies at DC (60 V nominal, 72 V max), so it also covers control-circuit protection in DC bus systems.
What the ratings mean for fit
The C-curve trips magnetically at 5 to 10 times rated current, which is the standard choice for mixed resistive-inductive loads in a panel — it won't pop on a motor's starting surge but clears fast on a hard fault. Energy limitation class 3 means it limits let-through energy enough to protect downstream wiring and devices in a properly coordinated system. Pollution degree 3 and overvoltage category III suit it for fixed-installation panels where conductive dust or condensation is present — typical for mill electrical rooms and industrial MCCs. The IP20 rating (with conductors connected) is standard for enclosed panel mounting; no special sealing needed inside a cabinet. The 72 mm width (4 modular units) and 70 mm installation depth fit standard DIN-rail enclosures. Mounting position is unrestricted, and the quick-assembly system clips onto the rail without tools. Combined terminals top and bottom accept supply from either end — no need to flip the breaker for top-feed vs bottom-feed.
Compliance and documentation
The breaker carries approvals to IEC/EN 60898-1, IEC/EN 60947-2, and UL 1077 / CSA C22.2 No.235 (5 kA under UL/CSA). It's halogen-free and silicon-free, which matters for panels in clean-room or corrosive environments where outgassing can't be tolerated. The sealable design allows the installer to lock the toggle position after commissioning.