Product Overview

The Siemens 6AG1931-2EC21-2AA0 is a SIPLUS PS DC-UPS module designed to provide uninterrupted 24 V DC power to industrial automation equipment. It belongs to the Siemens SIPLUS power supply product family and is based on the standard 6EP1931-2EC21 platform.

In industrial control systems, a stable 24 V DC supply is essential for PLCs, communication equipment, sensors, control relays, and other automation devices. A temporary power interruption can cause controllers to restart, communication links to drop, production sequences to stop, or important process data to be lost. A DC uninterruptible power supply module helps reduce these risks by maintaining the DC output through an external battery system when the normal power source fails.

The 6AG1931-2EC21-2AA0 operates with a nominal 24 V DC input and provides a rated output current of 15 A. It supports battery-based energy storage and automatically switches to buffering operation when the input voltage falls below the configured response threshold.

This model is part of the SIPLUS range, which is designed for applications requiring enhanced environmental resistance. Its specified configuration includes conformal coating and an extended operating temperature range of approximately -25°C to +60°C.

The module is suitable for industrial control cabinets, process automation installations, and other applications where maintaining a stable 24 V DC supply is important. It is particularly relevant to systems that need sufficient time for controlled shutdown, alarm transmission, or continued operation of selected control components during a power interruption.

Technical Specifications

Note: The supplied dimensions are retained as listing information. They may represent packaging or logistics dimensions rather than the module’s actual mounting dimensions. Confirm the physical dimensions before cabinet design.

Function and Working Principle

The Siemens 6AG1931-2EC21-2AA0 is designed to maintain a 24 V DC supply when the normal DC input becomes unavailable or falls below a defined voltage threshold. It works with an external battery system to provide temporary energy storage.

1. Normal Power Supply Operation

During normal operation, the module receives 24 V DC from an industrial power supply. It passes the regulated DC power to connected loads while monitoring the input voltage and battery condition.

The rated output current is 15 A, allowing the module to support a group of appropriately sized automation devices. The actual load current must remain within the module’s specified limits.

2. Automatic Battery Buffering

When the input voltage falls below the configured response threshold, the module switches to battery buffering operation.

The connected battery provides the energy required to maintain the DC output. This helps prevent an immediate loss of power to connected equipment during a temporary interruption.

The default response threshold is 22.5 V and can be adjusted between 22 V and 25.5 V in 0.5 V increments. The threshold should be selected according to the characteristics of the connected power supply and the requirements of the DC loads.

3. Battery Charging Management

The module includes a battery charging function with selectable charging-current settings of 0.35 A and 0.7 A. The factory setting is approximately 0.7 A.

The charging configuration should be matched to the connected battery system. Battery type, capacity, charging requirements, and manufacturer recommendations must be considered when designing the complete DC-UPS installation.

4. Output Voltage Regulation

The module provides a nominal 24 V DC output during normal operation and battery buffering.

In buffering mode, the specified output voltage range is 19–28.5 V DC. This range should be checked against the minimum operating voltage of connected equipment, especially for sensitive PLCs, communication devices, and instrumentation.

5. Protection and Monitoring

The module includes short-circuit protection and protection against reverse polarity at the input and energy-storage connections.

These functions help protect the power supply arrangement against certain wiring and electrical faults. Correct wiring, appropriate upstream protection, and regular inspection remain necessary for safe operation.

Role in Industrial Automation Systems

The 6AG1931-2EC21-2AA0 is typically installed between a 24 V DC power supply and the automation loads that require temporary backup power.

Its purpose is not simply to provide another source of DC power. It helps maintain the availability of essential control equipment during interruptions, supporting more predictable machine and process behavior.

PLC Power Continuity

PLCs are central components in many industrial automation systems. They process input signals, execute control logic, and generate output commands for machines and process equipment.

A power interruption can cause a PLC to restart or lose its ability to control the process. A DC-UPS module can provide temporary backup power to a compatible PLC supply circuit, helping maintain controller operation during short interruptions.

The actual backup duration depends on the battery capacity and connected load.

Industrial Communication Equipment

Industrial networks connect PLCs, remote I/O stations, HMIs, drives, and supervisory systems. A loss of power to network equipment may interrupt communication between control devices.

By maintaining the 24 V DC supply to selected network components, the DC-UPS module can help preserve communication availability during a power interruption.

Sensor and Instrumentation Support

Many industrial sensors and transmitters operate from a 24 V DC supply. Maintaining power to selected instrumentation can help preserve process information and support controlled shutdown procedures.

The designer should prioritize essential instruments and calculate the total load current before connecting them to the backup supply.

Alarm and Shutdown Systems

Some control systems need to maintain alarm indication, status monitoring, or shutdown-related functions after the main supply is interrupted.

A DC-UPS module can support these functions when the connected equipment is compatible with the available output voltage and backup duration.

It should not be treated as a replacement for a dedicated safety power system unless the complete design has been assessed and approved for that purpose.

Industrial Applications

1. PLC Control Cabinets

PLC cabinets commonly contain controllers, I/O modules, communication devices, relays, and signal-conditioning equipment. Many of these components rely on a 24 V DC supply.

The 6AG1931-2EC21-2AA0 can provide battery buffering for selected loads, helping prevent unnecessary controller resets and reducing the risk of interrupted control sequences.

2. Process Automation Systems

Chemical processing, water treatment, energy production, and other process industries often rely on continuous monitoring and control.

A temporary loss of DC power can interrupt instrumentation and communication. A DC-UPS module can help maintain essential control circuits while operators or backup power systems respond to the interruption.

3. Manufacturing Production Lines

Automated production lines may contain multiple controllers, sensors, operator panels, and communication devices. A short power interruption can stop a production sequence and require manual recovery.

Using a DC-UPS module for selected control loads can help reduce the impact of short-duration interruptions and support more orderly recovery.

4. Industrial Communication Cabinets

Industrial Ethernet switches and communication devices often require a stable 24 V DC supply. Maintaining their power can help preserve communication between automation equipment during temporary supply disturbances.

The actual connected load should be checked against the 15 A rated output.

5. Utility and Infrastructure Control

Water distribution, pumping stations, electrical infrastructure, and remote monitoring installations may require stable DC power for controllers and communication devices.

A battery-backed DC supply can help maintain selected control functions when the normal power source is interrupted.

6. Environmental and Industrial Facilities

The SIPLUS configuration is designed for an extended temperature range and includes conformal coating. These characteristics can be useful in industrial environments where operating conditions are more demanding than those typically encountered in standard indoor control cabinets.

The specified environmental range does not eliminate the need to consider humidity, condensation, chemical exposure, ventilation, and cabinet protection.

Installation and System Integration

Correct installation is essential for reliable DC buffering and battery operation.

1. Verify the Input Power Supply

The module requires a nominal 24 V DC input and supports an input range of 22–29 V DC.

Before installation, verify that the upstream power supply can provide sufficient current for both the connected loads and the battery-charging requirements.

The input current at the rated operating point is 15 A, with approximately 1 A additional current possible when the battery is empty. The power supply should therefore be selected with suitable capacity.

2. Select the Appropriate Battery System

The DC-UPS module requires an external battery system. Backup time depends on battery capacity, battery condition, load current, and operating temperature.

When selecting a battery, calculate the required backup duration and ensure that the battery voltage and charging characteristics are compatible with the module.

Do not assume that the UPS module includes a battery. Verify the complete order configuration before installation.

3. Configure the Buffering Threshold

The preset buffering response threshold is 22.5 V. The threshold can be adjusted between 22 V and 25.5 V.

A suitable threshold should be selected according to the upstream power supply’s behavior and the minimum acceptable voltage for the connected loads.

4. Configure Battery Charging

The module supports charging-current settings of 0.35 A and 0.7 A. Select the appropriate setting according to the connected battery manufacturer’s recommendations.

Incorrect charging settings can affect battery service life and reliability.

5. Install on the DIN Rail

The module is designed for DIN rail mounting. The standard mounting arrangement allows it to be installed alongside compatible power supply and automation components.

The published module dimensions should be used when planning cabinet space. The supplied listing dimensions of 135 × 140 × 70 mm should be confirmed because packaging dimensions may differ from the actual housing dimensions.

Allow sufficient space for wiring, ventilation, and maintenance access.

6. Connect the DC Loads

Connect the 24 V DC input, output, battery, and control or status connections according to the wiring diagram.

The total load current must not exceed the rated output current of 15 A. Consider startup current and transient load conditions when calculating the system’s electrical requirements.

7. Test the Backup Function

After installation, verify normal power operation, battery charging, and automatic transition to buffering mode.

A controlled power-interruption test can help confirm that the connected loads remain operational and that the available backup duration meets the application requirement.

Document the final wiring, threshold settings, charging-current configuration, battery information, and test results.

Compatible System Components

The 6AG1931-2EC21-2AA0 is intended to operate as part of a complete 24 V DC backup power system.

The presence of a component in this table does not mean it is included with the UPS module. Check the complete bill of materials before purchasing.

Alternative Models and Replacement Considerations

The 6AG1931-2EC21-2AA0 is a SIPLUS version based on the standard Siemens 6EP1931-2EC21 platform. When considering a replacement, engineers should compare electrical characteristics and environmental requirements.

A replacement should be assessed against the following factors:

• Nominal input and output voltage.
• Rated and peak output current.
• Battery voltage and capacity.
• Battery charging-current requirements.
• Buffering response threshold.
• Required backup duration.
• Environmental operating temperature.
• Conformal coating and environmental protection.
• Mounting dimensions and terminal arrangement.
• Status signaling and monitoring requirements.

A standard 24 V power supply is not automatically a suitable substitute for a DC-UPS module. The replacement must provide the required battery-buffering function.

Key Advantages

Continuous 24 V DC Buffering

The module helps maintain the DC supply to selected industrial loads when the normal input power is interrupted.

15 A Rated Output

The 15 A rated output supports a group of appropriately sized automation devices within the module’s electrical limits.

Adjustable Buffering Threshold

The response threshold can be adjusted between 22 V and 25.5 V, allowing the system to be configured according to the power supply and connected loads.

Battery Charging Function

Selectable charging-current settings support integration with a compatible external battery system.

Extended Temperature Range

The SIPLUS configuration supports an operating temperature range of approximately -25°C to +60°C.

Conformal Coating

The coated electronic assembly is designed to provide enhanced protection under specified environmental conditions.

Modular DIN Rail Installation

DIN rail mounting supports installation in modular industrial control cabinets alongside compatible power supply and automation components.

Protection Functions

Short-circuit and reverse-polarity protection help improve the reliability of the DC power arrangement when correctly installed.

Technical FAQs

1. What is the Siemens 6AG1931-2EC21-2AA0 used for?

It is a SIPLUS PS DC-UPS module used to maintain a 24 V DC supply during temporary power interruptions. It works with an external battery system.

2. What is the rated output current?

The rated output current is 15 A. The maximum connected load must remain within the specified current limits.

3. What input voltage does this module support?

It has a nominal input voltage of 24 V DC and supports an input range of 22–29 V DC.

4. Does the module include a battery?

The module is designed to operate with an external battery system. Confirm whether a compatible battery is included in the supplied package.

5. How long can it provide backup power?

Backup duration depends on battery capacity, battery condition, connected load current, and operating conditions. The module itself does not determine a fixed backup time.

6. What is the battery charging current?

The module supports charging-current settings of 0.35 A and 0.7 A. The factory setting is approximately 0.7 A.

7. What is the operating temperature range?

The specified SIPLUS configuration supports approximately -25°C to +60°C.

8. What is the difference between 6AG1931-2EC21-2AA0 and 6EP1931-2EC21?

The 6AG1931-2EC21-2AA0 is a SIPLUS version based on the 6EP1931-2EC21 platform. It includes conformal coating and an extended temperature range for more demanding environmental conditions.

9. Can it supply a PLC and communication equipment simultaneously?

Yes, provided the combined load remains within the 15 A output rating and the battery capacity is sufficient for the required backup time.

10. What should be checked before purchasing?

Verify the complete model number, input and output ratings, physical condition, battery compatibility, terminal condition, and included accessories. Also confirm whether the listed dimensions represent the module itself or its packaging.

Procurement and Maintenance Recommendations

When purchasing the Siemens 6AG1931-2EC21-2AA0, verify the complete article number and confirm that the SIPLUS environmental specification is appropriate for the intended installation.

For replacement projects, compare the 24 V DC input range, 15 A output rating, buffering threshold, charging-current settings, battery arrangement, and terminal connections. A standard DC power supply or a different DC-UPS model should not be treated as a direct replacement without technical review.

Before installation, inspect the housing, terminals, and mounting arrangement. Confirm that the external battery is compatible and that its capacity meets the required backup duration.

During maintenance, check battery condition, charging performance, terminal tightness, operating temperature, and status indications. Battery service life is affected by temperature, charging conditions, discharge depth, and maintenance practices.

For critical control systems, document the connected loads and test the actual backup duration periodically. This helps ensure that the DC-UPS arrangement continues to meet the operational requirements of the automation system.

Conclusion

The Siemens 6AG1931-2EC21-2AA0 SIPLUS PS DC-UPS 24 V/15 A is designed to provide battery-backed 24 V DC power for industrial automation systems. With a rated output current of 15 A, adjustable buffering thresholds, selectable battery charging current, conformal coating, and an extended operating temperature range, it supports applications where maintaining DC power continuity is important.

For PLC cabinets, process automation installations, industrial communication systems, and other control applications, correct battery selection and load calculation are essential. Verifying the complete model number, installation dimensions, and system requirements helps ensure reliable integration and effective power protection.