Siemens 6ES5951-7LD12 Power Supply Module

This module delivers stable DC power to the backplane and connected I/O cards. The Siemens 6ES5951-7LD12 converts AC line voltage into regulated 24 V and 5 V outputs. It measures 232 mm in width and 75 mm in height. This unit weighs approximately 1.6 kg for secure rack mounting.

Technical Specifications Table

Parameter	Value
Product Model	Siemens 6ES5951-7LD12
Category	Power Supply Module
Input Voltage	120/230 V AC (switchable via jumper)
Input Frequency	50/60 Hz
Output Voltage 1	24 V DC
Output Current 1	2 A
Output Voltage 2	5 V DC
Output Current 2	8 A
Total Output Power	88 W maximum
Dimensions (W x H x D)	232 mm x 75 mm x 130 mm
Weight	1.6 kg
Connection Type	2 x screw terminal blocks (rear)
Internal Components	1 x transformer, 1 x rectifier, 6 x filtering capacitors
Energy Storage	6 x 3300 µF electrolytic capacitors (total 19800 µF)
Hold-up Time	25 ms at full load
Efficiency	83% typical
Protection Features	Short circuit, overload, overvoltage, overtemperature

Internal Design and Power Distribution

This power supply uses a single step-down transformer with dual secondary windings. A full-bridge rectifier converts AC to DC for both output rails. The Siemens 6ES5951-7LD12 employs six large filtering capacitors for energy storage. These capacitors provide 25 ms of hold-up time during short power interruptions. The 5 V DC output powers the backplane and all logic modules. The 24 V DC output supplies sensor power and relay circuits separately.

Installation and Connection Guide

First, mount this power supply into the leftmost slot of your SIMATIC S5 rack. Next, select the correct input voltage using the internal jumper (120 V or 230 V). Then, connect your AC mains wires to the L, N, and PE terminals on the rear block. Wire the 5 V output to your backplane distribution points for logic power. Use the 24 V output for field devices like sensors, relays, and actuators. The module includes green LEDs for output status monitoring. This unit works with all SIMATIC S5 racks including 115U, 135U, and 155U models. Replace the unit immediately if the fan fails or unusual noise occurs.