What This BaseUnit Does in a Panel
The Siemens 3RK1908-0AP00-0BH0 is a SIMATIC BaseUnit designed specifically for DC feed-in in an automation cabinet. It distributes a 24 VDC supply (rated 20.4 V minimum, 28.8 V maximum) to the modules mounted above it on a standard DIN rail, with a maximum ampacity of 7 A. That 7 A is the total current the BaseUnit can pass to the downstream I/O slices — size your module load so the sum across all connected slices stays under that figure, or you'll need a second feed point. The push-in terminals (spring-loaded, main and auxiliary/control circuits) accept solid or finely stranded wire 1x 0.5 to 2.5 mm²; a standard slot screwdriver 0.6 x 3.5 mm opens the clamp. Mounting position can be vertical or horizontal, and the 30 mm width means it takes up one standard slot on the rail.
Pollution degree 2 — normal factory floor, not conductive dust or condensation. Shock resistance is 6g for 11 ms; vibration resistance is 15 mm amplitude to 6 Hz, then 2g to 500 Hz. That covers most conveyor and machine-tool environments. Clearance above and below the unit is 50 mm each side for airflow and wiring access.