The Siemens 5SJ3650-7 is a SENTRON 5SJ3 miniature circuit breaker — 4-pole (3P+N), C-curve, rated 50 A at 400 V AC with a 4.5 kA breaking capacity certified to both EN 60898 and IEC 60947-2. That 4.5 kA figure is the fault-clearing limit it holds the unit on the grid through; anything beyond that and the upstream device needs to coordinate. The C-curve characteristic means it trips between 5 and 10 times rated current — standard for motor-starting and transformer inrush loads where you need to ride through the magnetizing spike without nuisance tripping.
Terminal and wiring
Terminals accept solid or stranded conductors from 0.75 mm² up to 25 mm², which covers the full range from control-circuit tails up to the main feeder for a 50 A sub-distribution board. The unit is sealable — a lead seal can be fitted over the terminal cover to prevent tamper after commissioning, a common requirement on utility-metered or safety-critical supplies. Halogen-free and silicon-free construction matters if this breaker sits in a confined enclosure where outgassing from a fault arc could corrode adjacent contacts or sensitive electronics.
Panel fit and environment
Occupies 4 width units (roughly 72 mm) on the DIN rail, with an installation depth of 70 mm. Mounting position is any — no derating needed for horizontal or inverted orientation, which simplifies layout in a crowded gland plate. Ambient range is -20 to +45 °C operating, with a storage range of -40 to +75 °C. IP20 with connected conductors is the standard for enclosed distribution boards; not rated for washdown or outdoor exposure without a secondary enclosure. Mechanical life is 20 000 switching cycles — that is the handle mechanism, not the electrical endurance under fault, but it gives a sense of the build quality for routine isolation duty.