What it is and what it does
The Siemens 6ES7405-0KR00-0AA0 is a SIMATIC S7-400 power supply module — the PS405 wide-range unit that takes 24, 48, or 60 V DC input and delivers 5 V DC at up to 10 A to the backplane bus. It occupies 2 slots in the rack and is designed for redundant configurations, meaning you can pair two units for N+1 or 1+1 redundancy without extra hardware. The 5 V DC rail feeds the CPU and I/O modules; the 24 V DC backplane bus is also supported at 1 A for external loads like interface modules.
Key ratings and what they mean for your panel
The headline number is the 10 A at 5 V DC for the backplane bus — that's the total current available to power all S7-400 modules in the rack. A base load of 200 mA is required just to keep the bus alive. The input side is flexible: at 24 V DC it draws 4.5 A, at 48 V DC it draws 2.1 A, and at 60 V DC it draws 1.7 A. That wide-range input means the same part works on 24 V control panels or higher-voltage DC plants without a step-down converter. Inrush current hits 18 A for 20 ms at full width at half maximum — enough to trip a fast-acting breaker if the upstream protection isn't coordinated. The module includes short-circuit protection on the output, so a fault on the 5 V rail won't cascade into the input supply. Typical power loss is 29 W, which adds to the panel's thermal load; plan ventilation accordingly. Mains buffering holds the output for 20 ms on a voltage failure, and it meets NAMUR recommendation for process plants where ride-through is critical. An optional backup battery (2x lithium AA, 3.6 V / 1.9 Ah) keeps the internal real-time clock and SRAM alive during extended outages.
Where it fits and how it connects
Physically, the module is 290 mm high, 50 mm wide, and 217 mm deep — it slides into a standard S7-400 rack and requires 2 slot positions. The electrical connection uses 3x 1.5 mm² solid or stranded wire with end sleeves, accepting an external diameter of 3 mm to 9 mm. Equipment protection class I means a protective earth conductor is mandatory. FM approval is on file: up to 40 °C the temperature class is T4, so the module is suitable for installation in Class I, Division 2 hazardous locations (gas groups A, B, C, D) within that temperature limit. This is a key differentiator for process and refinery panels where ordinary power supplies would require external purging.