SIEMENS 6ES5185-3UA13 Power Supply Unit

Product Overview

The SIEMENS 6ES5185-3UA13 is a complete expansion unit (EU 185) with an integrated power supply, purpose-built for the SIMATIC S5 family of programmable logic controllers. As part of the S5-185U series, this unit is designed to expand the I/O capacity of central controllers such as the S5-115U, S5-135U, and S5-155U by providing 21 standard S5 module slots and a robust power delivery system. The SIEMENS 6ES5185-3UA13 transforms an incoming 120/230 V AC supply into a regulated 5 V DC output capable of delivering 18 A to the backplane bus, ensuring stable operation for all installed CPU, communication, and I/O modules.

The integrated power supply within the SIEMENS 6ES5185-3UA13 also provides an auxiliary 24 V DC output with coarse stabilization for powering field devices such as sensors and actuators, further simplifying system architecture. To ensure reliable operation even in warm industrial environments, the unit is equipped with a built-in cooling fan, complete with a fan failure monitoring LED and a relay contact for remote alarm signaling. While the SIMATIC S5 series has been discontinued for many years, the SIEMENS 6ES5185-3UA13 remains an essential component for maintaining the longevity of existing automation assets in industries where full system migration is not yet feasible.

Technical Specifications

Parameter Name	Parameter Value
Product Model	6ES5185-3UA13
Manufacturer	Siemens
Product Type	S5-185U Expansion Unit with Integrated Power Supply
Series	SIMATIC S5
Input Voltage	120 V AC (85–132 V) / 230 V AC (176–264 V), selectable
Input Frequency	50 / 60 Hz
Output – Backplane Bus	5 V DC, 18 A (regulated)
Output – Auxiliary	24 V DC (coarse stabilization, approx. 1–2.8 A)
Module Slots	21 standard S5 module slots
Cooling Method	Built-in fan with failure monitoring LED and alarm relay
Working Temperature	0 °C to +55 °C
Protection Class	IP20
Dimensions (W x H x D)	Approx. 482.6 x 267 x 220 mm (19″ rack mount)

Main Features and Advantages

Integrated Power and Expansion in One Unit

The SIEMENS 6ES5185-3UA13 eliminates the need for a separate power supply module by integrating a high-capacity AC-to-DC converter directly into the expansion rack. This all-in-one design saves valuable cabinet space and simplifies procurement. The regulated 5 V DC output at 18 A provides ample power for dense configurations of up to 21 additional S5 modules, making it a practical and cost-effective solution for system expansion.

Robust Thermal Management and Diagnostics

A key advantage of the SIEMENS 6ES5185-3UA13 is its active cooling system. The built-in fan ensures consistent airflow across installed modules, maintaining operational stability even in warm environments. The fan is equipped with a monitoring LED and a relay contact output, allowing the unit to report a fan failure directly to a central control system. This feature is invaluable for predictive maintenance, enabling early intervention before a thermal issue can compromise the entire expansion rack.

Designed for Legacy System Longevity

While the product has been discontinued, the SIEMENS 6ES5185-3UA13 represents a critical resource for facilities operating legacy SIMATIC S5 automation. Its construction adheres to the rigorous quality and safety standards typical of Siemens, including safe electrical separation according to VDE 0805/EN 60950. For maintenance engineers, the availability of this unit—even as a spare—is essential to keep production lines running while planning a strategic migration to modern control platforms like S7.