The Siemens 3NJ6312-3AE0.-.... is a SENTRON 3NJ63 switch disconnector with fuses in an in-line design, pluggable NH1 size rated 250 A. It's a 2-pole unit rated for DC23B duty at 230 V with a 100 kA breaking capacity at DC230V — that's the fault current it can safely interrupt without welding or arc flash propagating upstream. The manual operating mechanism includes EFM 25 electronic fuse monitoring, so you get a signal when a fuse blows rather than chasing a dead circuit. This sits in the SENTRON 3NJ63 family, Siemens' modular fuse-switch line for DC distribution and motor feeder isolation. The NH1 fuse size (250 A max) is common in industrial DC bus panels, battery banks, and UPS bypass circuits.
RoHS compliance is confirmed since 27 September 2019. REACH Article 33 candidate list information is available on request.
In-line design means the line and load connections are opposite each other — plan your busbar or cable routing accordingly. Pluggable NH1 fuse bases let you swap fuse links without tools, but the switch body itself is a fixed mount. The manual operating handle needs clearance for the switching arc and for the EFM 25 monitoring module wiring. Rated for DC23B at 230V — that's the utilization category for DC switching of resistive and mixed loads with some inductance. If your load is purely resistive (DC1), you can push the current higher, but stay within the NH1 fuse rating.