What this MCB is and where it fits
The Siemens SENTRON 5SJ4245-7HG41 is a 2-pole miniature circuit breaker with C tripping characteristic, rated 45 A at both 30 °C and 40 °C ambient. It snaps onto standard DIN rail (35 mm) and accepts any mounting position, so it drops into existing panel layouts without rework. The 36 mm width (2 modular units) and 70 mm depth match the 5SJ4 family footprint — a direct swap for an earlier 5SJ4 unit or a drop-in for a panel originally built around the 5SL6550-7BB, provided the terminal arrangement (combined screw terminals top and bottom, no tunnel terminals) is compatible.
Rated current and thermal derating
Rated 45 A at 40 °C — the same as at 30 °C, so no early derating in a warm panel. Above 40 °C the curve steps down: 44.1 A at 45 °C, 43.2 A at 50 °C, 42.2 A at 55 °C, 41.4 A at 60 °C. That means a 45 A circuit at 50 °C still holds 96 % of its rating; a designer sizing for a 50 °C panel ambient can treat it as a 43 A breaker without over-specifying.
Environmental and mounting constraints
Pollution degree 3 and overvoltage category 3 — standard for fixed-installation distribution panels in industrial environments. The housing is halogen-free and silicon-free, which matters for clean-room or semiconductor-adjacent lines where outgassing is a concern. IP20 with connected conductors, IP40 in the handle area; not rated for washdown, so keep it inside a sealed enclosure in wet areas. Vibration resistance tested to 50 m/s² at 25–150 Hz and 60 m/s² at 35 Hz (4 s) — adequate for machine-mounted panels on pumps or compressors.
Lifecycle and sourcing
Listed as current-production lifecycle stage. No end-of-life notice or successor code found. Sourced and quoted to order against an RFQ through independent distribution.