The Siemens 6ES7407-0DA01-0AA0 is a SIMATIC S7-400 PS407 power supply delivering 5 V DC at 4 A from a 120/230 V AC mains input. It occupies one slot in the S7-400 rack and provides the backplane bus with up to 4 A at 5 V DC, with a 100 mA base load required to hold regulation. The 24 V DC backplane bus is also supplied at up to 0.5 A, idling-proof.
The 4 A at 5 V DC is the headline number — it tells you how many S7-400 modules this supply can feed. Each module draws from the 5 V backplane; if your rack exceeds 4 A total draw, you'll need a second supply or a higher-rated PS407 variant. The 24 V DC output at 0.5 A covers the I/O bus and is idling-proof, meaning it won't drop out under light load. The supply handles 47 Hz to 63 Hz input frequency, so it works on 50 Hz and 60 Hz mains without derating. Mains buffering holds the output for 20 ms on a voltage dip — enough to ride through a brief sag without dropping the CPU. It also complies with NAMUR recommendation for mains/voltage failure stored energy time, which matters in process plants where a brownout can cause a nuisance trip.
This is a standard S7-400 power supply module. It snaps into the rack and connects to the backplane automatically — no wiring to the bus. The AC input connects via a 3-wire terminal accepting 1.5 mm² solid or stranded wire with end sleeve, external diameter 3 mm to 9 mm. Equipment protection class I requires a protective conductor.
FM approval is present, rated Ta: 0 °C to 60 °C T4 — suitable for hazardous locations where gas group T4 equipment is permitted. Short-circuit protection is built in. An optional backup battery (1x lithium AA, 3.6 V / 2.3 Ah) can be fitted to maintain memory in the CPU during a power loss.