What it is and where it fits
The Siemens 5SY8450-7 is a 4-pole SENTRON miniature circuit breaker with a C-curve trip characteristic, rated 50 A at 440 V AC. It snaps onto a DIN rail — any mounting position works — and occupies 4 modular width units (72 mm wide). The 25 kA breaking capacity per IEC 60947-2 means it can safely interrupt faults up to that level on a 440 V AC industrial supply without cascading upstream. For DC circuits it's rated 15 kA at 72 V, so it handles battery-bank or rectifier faults in the same panel. The C-curve (tripping between 5 and 10 times rated current) is the standard choice for motor-starter and transformer inrush loads — it holds through the magnetizing spike but clears a hard short fast. Rated current is 50 A at 45 °C; at 55 °C it derates to 47.85 A, and at 50 °C it's 48.95 A, so plan the load at the panel's ambient temperature, not the breaker's label.
Panel integration notes
Depth is 76 mm (70 mm installation depth behind the panel), height 90 mm. The quick-assembly fastening system means it clips onto the DIN rail without tools and the combined top/bottom terminals accept both busbar and wire — no need to swap terminal types between incoming and outgoing. Pollution degree 3 and overvoltage category III suit it for industrial control panels where conductive dust and transient surges are expected. IP20 with connected conductors — fine inside a closed enclosure, not for wet areas. Sealable, halogen-free, silicon-free — relevant if the panel goes into a food-processing or semiconductor fab environment where outgassing or tamper-proofing is specified. Vibration resistance per IEC 60068-2-6 covers ±1 mm at 5–25 Hz and 50 m/s² at 25–150 Hz, so it holds up on a machine frame or conveyor line.
Compliance and documentation
Designed for mechanical engineering and industry per the manufacturer's suitability statement. The product designation follows EN 61346-2 and IEC 81346-2 function code F (protective device). Touch protection is built in — no exposed live parts when wired. Humidity limits: 95% up to 55 °C, 55% up to 70 °C, 35% up to 75 °C. The neutral conductor is not switched (solid neutral through the 4-pole frame).