Siemens 6ES7 405-0RA02-0AA0 PS 405 Power Supply for S7-400

The 6ES7 405-0RA02-0AA0 (PS 405 10A) is a power supply module for the Siemens S7-400 automation system. It converts 120/230 VAC or 125-250 VDC to a regulated 24 VDC output (10 A continuous) for powering the backplane bus and CPU. The module includes a battery backup port for external 24 V battery, ensuring data retention during mains loss.

Electrical Specifications

• Input Voltage: 120/230 VAC (automatic range switching) or 125-250 VDC

• Output Voltage: 24 VDC ±3% adjustable via potentiometer (22.8 – 26.4 VDC)

• Output Current: 10 A continuous (12 A peak for 5 seconds)

• Efficiency: 92% at rated load

• Ripple:<50 mVpp

• Hold-up Time: 20 ms at full load

Protection Features

The PS 405 incorporates overvoltage protection (crowbar circuit), overload protection (hiccup mode with auto-recovery), and short-circuit protection (current limiting). An LED indicator displays output OK (green). The module also has a built-in temperature sensor that reduces output current if internal temperature exceeds 85°C, preventing shutdown.

Battery Backup Function

A 2-pin terminal allows connection of an external lead-acid or lithium battery (e.g., 6ES7971-0BA00). When mains fails, the PS 405 seamlessly switches to battery power, supplying the CPU RAM and real-time clock for up to 3 months (depending on battery capacity). The module charges the battery automatically when mains is present (float charge, max 0.5 A).

Mechanical and Environmental

Dimensions: 25 mm width (1 slot) x 290 mm height x 130 mm depth. Weight: 0.8 kg. Mounting: screw into S7-400 rack. Operating temperature: 0°C to 60°C; storage: -40°C to 85°C; humidity: 5–95% non-condensing. Vibration: 0.3g at 10-58Hz; shock: 5g. Protection class IP20. The module is rated for pollution degree 2.

Compatibility and Certifications

Works with all S7-400 racks (UR1, UR2, UR2-H, CR3). Compatible with CPUs 412, 414, 416, 417 series. Certifications: CE, UL 508, CSA, ATEX (Zone 2), IECEx, and marine approvals (GL, DNV). The module is RoHS compliant and has a MTBF of 1.2 million hours (per Siemens reliability data).