PS405 power supply for S7-400 racks
The Siemens 6ES7405-0KA02-0AA0 is the PS405 wide-range power supply for the SIMATIC S7-400 rack system, accepting 24 V DC, 48 V DC, or 60 V DC input and delivering a regulated 5 V DC output at 10 A to the backplane bus. It occupies two slots on the rack and requires no base load on the 5 V DC backplane bus, which simplifies commissioning when the rack is partially populated. The unit is rated for continuous operation from 0 °C to 60 °C ambient, with an FM approval at T4 temperature class, and carries BIS and CCC certifications for global project deployment.
Backplane current and hold-up performance
The 5 V DC backplane bus is rated at 10 A maximum, with an additional 1 A available at 24 V DC for the backplane — both rails are idling-proof, meaning the supply regulates correctly even with zero load. Mains buffering holds the output for 20 ms on voltage failure, and the design meets NAMUR recommendation for process industry ride-through requirements. Inrush current is limited to 18 A peak with a 20 ms half-width pulse, which keeps the upstream breaker selection straightforward — a standard C-curve MCB on the DC feed handles it without nuisance tripping.
Input voltage flexibility and output ratings
The PS405 accepts three nominal DC input voltages, with corresponding output current ratings: 4 A at 24 V DC input, 2 A at 48 V DC, and 1.6 A at 60 V DC. Typical active power input is 95 W with a 20 W power loss, so the unit runs cool enough that adjacent slot modules aren't thermally stressed in a standard 290 mm rack. An optional backup battery pack (2x lithium AA, 3.6 V / 2.2 Ah) can be fitted to maintain the backplane buffer during extended power outages.
The module measures 50 mm wide by 290 mm high by 217 mm deep, occupying two rack slots — verify slot availability before specifying. Power connection uses 3x 1.5 mm² solid or stranded wire with end sleeves, accepting an external cable diameter of 3 mm to 9 mm. Equipment protection class I requires a protective conductor connection. Overvoltage category II applies, so the supply is intended for installation within a panel where transient overvoltages are limited by upstream distribution.