Siemens 6ES5955-3LF12 Simatic S5 Power Supply Unit

The Siemens 6ES5955-3LF12 is a robust, high-performance power supply unit designed for the Simatic S5 automation family. This unit provides reliable power distribution for central controllers and expansion racks, including the S5-135U, 150U, 155E, and 185U series. It is engineered to maintain stable 5 VDC logic power in demanding industrial environments, ensuring consistent operation of backplane processors and I/O modules.

Features

• High Current Capacity: Delivers a maximum continuous output of 40 A at 5 VDC, supporting high-density rack configurations.
• Flexible Input: Configurable via user-selectable links for either 115 VAC or 230 VAC single-phase power grids.
• Integrated Protection: Features built-in overvoltage protection (OVP) and overcurrent protection (OCP) to safeguard rack components against faults.
• Galvanic Isolation: Engineered with high-integrity isolation barriers to prevent field-side electrical noise from affecting control logic.
• Thermal Management: Equipped with heavy-duty heat sinks and designed for standard rack-based airflow to maintain stability under load.

Applications

This power supply is essential for maintaining legacy Simatic S5 installations, commonly found in heavy industrial sectors such as metal rolling mills, chemical processing facilities, and automated logistics/container terminals. It acts as a critical spare to prevent unplanned downtime in systems where S5 controllers manage complex, continuous processes.

Technical Specifications

Installation Guidelines

• Power Disconnection: Always ensure the primary AC input is fully disconnected before installing or removing the module from the rack.
• Mounting: Ensure the unit is securely seated within the designated S5 chassis slot to maintain proper electrical contact with the backplane.
• Cooling: Maintain clear airflow paths around the module heat sinks; do not obstruct ventilation channels in the rack.
• Grounding: Verify that the chassis is properly grounded in accordance with industrial safety standards to prevent noise interference.
• Input Configuration: Confirm that the input voltage selection links are correctly set for the local facility voltage (115V or 230V) before applying power.

FAQ

Is this unit compatible with all S5 racks?

This power supply is specifically designed for the S5-135U, 150U, 155E, and 185U configurations. Please verify your rack model before installation.

What should I do if the OVP or OCP trips?

If the unit shuts down due to an overvoltage or overcurrent fault, inspect the rack backplane for short circuits or excessive load demands. After clearing the fault, the unit may require a power cycle to reset.