PS407 10A — what it delivers to the S7-400 backplane
The Siemens 6ES7407-0KA02-0AA0 is a PS407 power supply for the SIMATIC S7-400 rack. It accepts a wide-range input — 120 V AC, 230 V AC, 120 V DC, or 230 V DC — and outputs 5 V DC at up to 10 A to the backplane bus, with no base load required. A separate 24 V DC rail supplies up to 1 A for external I/O or interface modules, and it's idling-proof so you don't need a dummy load to keep regulation stable. The 5 V DC rail is the critical one for the S7-400 CPU and backplane — 10 A capacity means it can power a fully loaded rack with multiple high-current interface modules. The 24 V DC auxiliary output is a nice bonus for powering a small field device or an external relay panel without a separate supply.
This PS407 occupies 2 slots in the S7-400 rack. Its dimensions — 290 mm high, 50 mm wide, 217 mm deep — match the standard S7-400 form factor. The power connection uses 3x 1.5 mm² solid or stranded wire with end sleeve, accepting an external diameter of 3 mm to 9 mm. Equipment protection class I with a protective conductor means the chassis must be bonded to the panel ground. Overvoltage category II is standard for fixed-installation power supplies within a building's distribution network.
Environmental limits and approvals
Rated for 0 °C to 60 °C ambient. The FM approval covers Class I, Division 2 hazardous locations with a T4 temperature code at up to 70 °C ambient — note the FM rating extends the upper ambient to 70 °C, while the standard operating spec stops at 60 °C. That extra headroom matters if the supply is mounted near heat-generating modules in a non-incendive area. Typical power loss is 20 W. Active power input is 95 W typical. Inrush current hits 63 A for 1 ms at full width at half maximum — that's a brief spike, not a sustained draw, but it can trip a fast-acting MCB if the upstream breaker is undersized. Leakage current is 3.5 mA max.
Mains buffering and backup
Mains failure hold-up time is 20 ms — enough to ride through a half-cycle dropout at 50 Hz. The supply also supports mains buffering per NAMUR recommendation, which is relevant for process industry installations following NE 21 guidelines. An optional backup battery (1x lithium AA, 3.6 V / 2.2 Ah) can maintain the S7-400's internal real-time clock and RAM data during extended power loss. The battery is not included with the supply — order separately if you need memory retention.
No official successor order code has been published — the PS407 10A remains the current offering for this S7-400 power requirement.