PS407 power supply for S7-400 racks
The Siemens 6ES7407-0KR00-0AA0 is a PS407 power supply for the SIMATIC S7-400 system, delivering 10 A at 5 V DC to the backplane bus from a universal input accepting 120/230 V AC or 110/230 V DC. It occupies 2 slots in the rack and is explicitly designed for redundant configurations, meaning two units can share the load or back each other up without conflict on the backplane. The 5 V DC rail can supply up to 10 A, but requires a 200 mA base load to stay in regulation — a detail that matters during commissioning when the rack is partially populated. The 24 V DC rail provides up to 1 A and is idling-proof, so it won't drop out under light load.
Input flexibility and ride-through
Input range covers 120/230 V AC (47–63 Hz) and 110/230 V DC, with inrush current limited to 18 A (15x rated input current). On a mains failure, the unit holds up the output for 20 ms — enough to trigger a controlled shutdown or switch to the redundant partner. NAMUR buffering is supported for process-industry installations that require defined behavior on voltage dips. Power loss is 22.4 W typical, with active power input of 97.5 W typical at full load. That heat has to go somewhere — the 290 mm height and 217 mm depth provide enough surface area for convection cooling in a standard S7-400 rack, but clearance above and below the rack matters for airflow.
FM approval is present, rated T4 up to 40 °C ambient — relevant for installations in hazardous locations where the power supply sits outside the classified area but must not be an ignition source. Equipment protection class I with protective conductor connection is standard. The backup battery option uses 2x lithium AA cells at 3.6 V / 1.9 Ah to retain the real-time clock and RAM contents during a power-down.