Product Overview

The Siemens 6AG1961-3BA21-7AX0 SIPLUS PS E202U Redundancy Module is an industrial power supply accessory designed to improve the availability and reliability of 24 V DC power distribution systems. It is based on the Siemens 6EP1961-3BA21 redundancy module and incorporates conformal coating to provide additional protection for its electronic assembly in demanding industrial environments.

The module is designed to decouple two SITOP power supplies, allowing them to feed a common DC load while reducing the possibility that a fault or short circuit on one power supply branch will affect the other branch. This arrangement supports redundant power architectures in which continuity of the control-system supply is important.

The 6AG1961-3BA21-7AX0 operates with a 24 V DC nominal supply and accepts an input voltage range of 24–28.8 V DC. Its rated output current is 40 A, with a maximum aggregate output current of 40 A. It is suitable for applications using two SITOP power supplies with a maximum output current of 20 A each.

As part of the SIPLUS product family, this model is intended for installations that require additional environmental protection. Its conformal-coated electronics and specified operating temperature range of -40 to +70°C make it suitable for a wider range of industrial conditions than the corresponding standard configuration, subject to the manufacturer’s installation requirements.

The module also provides status indication and a relay signaling contact. These features allow maintenance personnel or a supervisory control system to monitor the condition of the two input power supply branches.

Technical Specifications

The dimensions and weight above are the supplied product-listing values. Confirm the physical unit and packaging configuration before using them for cabinet planning or shipping calculations.

Function and Working Principle

The primary function of the 6AG1961-3BA21-7AX0 is to provide redundancy between two 24 V DC power supply branches. It helps maintain a common DC output for connected automation equipment while electrically decoupling the individual power sources.

1. Dual Power Supply Decoupling

In a redundant power arrangement, two independent SITOP power supplies feed the redundancy module through separate input connections. The module combines these inputs into a common output while preventing an electrical fault on one input branch from directly affecting the other branch.

This arrangement is useful when a single power supply failure must not immediately interrupt the DC supply to critical control equipment.

The module is designed for two power supplies with a maximum output current of 20 A each. The combined output current must remain within the module’s maximum aggregate rating of 40 A.

2. Redundant 24 V DC Distribution

The module provides a nominal 24 V DC output for connected loads. Its output voltage is approximately 0.5 V below the input voltage because of the internal decoupling circuit.

This voltage characteristic should be considered when designing the DC distribution system. Engineers should verify that the connected PLCs, communication equipment, sensors, and other loads receive a voltage within their permitted operating ranges.

3. Fault Isolation

The decoupling function helps prevent a fault in one power supply branch from pulling down the other branch. If one supply fails or its output becomes abnormal, the remaining supply can continue supporting the connected load, provided that it has sufficient capacity.

The module does not generate backup energy. It depends on the availability and capacity of the connected power supplies.

4. Status Monitoring

The 6AG1961-3BA21-7AX0 includes LED status indication. A green LED indicates that both input voltages are above the switching threshold. A red LED indicates that at least one input voltage has fallen below the threshold.

The switching threshold can be adjusted within the specified 20–25 V range. This allows the monitoring function to be configured according to the requirements of the DC power system.

5. Relay Signaling

An isolated relay contact provides an additional status signal. The contact can be connected to a PLC digital input, alarm circuit, or supervisory monitoring system.

The relay indicates whether both input voltages are above the configured threshold. This allows the control system to identify a degraded redundant supply condition before a complete power interruption occurs.

Role in Industrial Automation Systems

Stable 24 V DC power is essential for many industrial automation devices. PLC CPUs, remote I/O stations, communication equipment, sensors, and control relays frequently depend on a continuous DC supply.

The 6AG1961-3BA21-7AX0 supports power availability by allowing two suitable power supplies to operate in a redundant arrangement.

PLC Power Supply Protection

A PLC system may control production equipment, process interlocks, motor starters, and safety-related signals. An unexpected interruption of its 24 V DC supply can stop the controller and disrupt the production process.

By using two independent power supplies with a redundancy module, engineers can reduce the risk of a single power supply failure interrupting the PLC’s DC supply.

Remote I/O and Field Device Distribution

Distributed automation systems often contain remote I/O stations and field devices located throughout a production facility. These devices may depend on a centralized 24 V DC distribution network.

The redundancy module can be installed in the power distribution section to support a more reliable supply arrangement for selected automation loads.

Industrial Communication Equipment

Industrial Ethernet switches, communication gateways, and network interface devices may also use 24 V DC power. A redundant power architecture can help maintain communication availability when one power supply branch becomes unavailable.

The module’s relay signal can be connected to the monitoring system to provide information about the condition of the redundant supply inputs.

Centralized Control Cabinets

In a centralized control cabinet, multiple automation components may share a DC power distribution system. The 6AG1961-3BA21-7AX0 can help establish a redundant power source for important control circuits.

The actual loads should be divided and protected according to their electrical requirements. A redundancy module does not replace branch circuit protection or proper power supply sizing.

Industrial Applications

The Siemens 6AG1961-3BA21-7AX0 can be used in industrial installations where maintaining a stable 24 V DC supply is important.

1. Manufacturing Automation

Automated production lines depend on PLCs, sensors, actuators, and communication equipment to coordinate machine operation. A redundant power arrangement can reduce the risk of production interruption caused by an individual power supply failure.

2. Process Control Systems

Chemical processing, water treatment, and other process industries use distributed control equipment that may require continuous DC power.

The module can support redundant supply arrangements for selected control and monitoring circuits. The overall design must account for load criticality and the availability of independent power sources.

3. Industrial Communication Networks

Communication equipment is often distributed across control cabinets and machine stations. Maintaining its power supply can help prevent unnecessary communication interruptions.

The module can be used to decouple two suitable power supplies feeding a common 24 V DC load.

4. Infrastructure and Utility Systems

Infrastructure installations may contain monitoring devices, PLC panels, and communication equipment that need reliable DC power. A redundant supply architecture can help improve the availability of these systems.

5. Machinery and Equipment Control

Individual machines may use 24 V DC power for controller electronics, sensors, relay circuits, and other control components. The redundancy module can be considered where the machine design requires an additional level of power supply availability.

Installation and System Integration

Correct installation is essential for reliable redundancy operation. The module must be connected to compatible power supplies and installed according to the specified electrical and environmental requirements.

1. Verify Power Supply Compatibility

Use two suitable SITOP power supplies with a nominal 24 V DC output. Each supply must not exceed the specified maximum output current of 20 A for this application.

Check the output voltage, current rating, protection characteristics, and operating condition of both power supplies before connecting them to the module.

2. Observe the Maximum Current Rating

The module has a rated output current of 40 A and a maximum aggregate current of 40 A.

The total connected load must remain within this limit. The load distribution should also be evaluated to ensure that the remaining power supply can support the required load if the other supply fails.

A redundancy module does not automatically double the available load capacity. Its purpose is to improve availability through decoupling, not to provide unrestricted additional output current.

3. DIN Rail Installation

The module is designed for mounting on a DIN rail conforming to EN 60715, with a 35 × 7.5 mm or 35 × 15 mm profile.

Install it in a suitable control cabinet with enough space for wiring, ventilation, inspection, and maintenance access. Follow the manufacturer’s clearance and mounting requirements.

4. Connect Input and Output Wiring

Connect the two power supply outputs to their designated input terminals and connect the common output to the DC distribution circuit.

Use conductors with appropriate cross-sectional areas and current ratings. Check terminal tightening torque and ensure that the polarity is correct.

Incorrect wiring may damage the module or connected equipment. Installation and servicing should be performed by qualified personnel with the supply isolated.

5. Configure the Monitoring Threshold

The module provides an adjustable switching threshold between 20 V and 25 V.

Select a suitable threshold according to the requirements of the connected equipment and the intended fault-monitoring strategy. Confirm the LED indications and relay response during commissioning.

6. Test Redundant Operation

After wiring, verify that both power supplies operate normally and that the output voltage remains within the permitted range.

A controlled test can be performed to check whether the remaining supply supports the load when one input supply is disconnected or switched off. Confirm the LED status and relay signaling response.

The test procedure must follow the manufacturer’s safety instructions and should not expose the connected equipment to an uncontrolled power interruption.

Compatible System Components

The 6AG1961-3BA21-7AX0 is intended to operate with compatible Siemens SITOP power supplies and 24 V DC automation equipment.

The listed components are examples of equipment that may be used in a complete power distribution system. They are not necessarily included with the redundancy module.

Alternative Models and Replacement Considerations

The 6AG1961-3BA21-7AX0 is a SIPLUS version based on the standard Siemens 6EP1961-3BA21 redundancy module.

Before choosing an alternative, compare:

• Nominal input and output voltage.
• Maximum input current per supply.
• Maximum aggregate output current.
• Decoupling and fault-isolation behavior.
• Switching threshold and monitoring functions.
• Relay contact rating and signaling logic.
• Operating temperature range.
• Conformal coating and environmental protection.
• DIN rail mounting and terminal arrangement.
• Physical dimensions and cabinet clearances.

A standard redundancy module should not automatically be treated as equivalent to a SIPLUS version. Environmental requirements and the exact electrical configuration must be considered.

Key Advantages

Redundant Power Supply Architecture

The module supports the use of two independent SITOP power supplies, helping reduce the risk of a single power supply failure interrupting the connected DC load.

24 V DC / 40 A Output

Its 40 A rated output supports industrial DC distribution systems with appropriately sized loads and compatible power supplies.

Input Decoupling

The decoupling function helps prevent a fault in one input branch from directly affecting the other power supply branch.

Conformal-Coated Electronics

The SIPLUS configuration includes conformal coating to provide additional protection for the electronic assembly in demanding environments.

Wide Operating Temperature Range

The specified operating temperature range of -40 to +70°C supports applications with more demanding ambient conditions, subject to the required mounting and cooling conditions.

Visual Status Indication

Green and red LEDs provide a straightforward indication of the condition of the two input voltage branches.

Relay-Based Monitoring

The isolated relay contact can provide a status signal to a PLC or supervisory system, supporting centralized fault monitoring.

DIN Rail Installation

The module uses a standard DIN rail mounting arrangement, allowing it to be installed in industrial control cabinets alongside compatible power supplies and distribution equipment.

Technical FAQs

1. What is the Siemens 6AG1961-3BA21-7AX0?

It is a SIPLUS PS E202U redundancy module designed to decouple two 24 V DC SITOP power supplies. It supports a redundant power arrangement for industrial control and automation equipment.

2. What is the input voltage range?

The module accepts an input voltage range of 24–28.8 V DC. Its nominal supply voltage is 24 V DC.

3. What is the rated output current?

The rated output current is 40 A, with a maximum aggregate current of 40 A. The intended configuration uses two SITOP power supplies with a maximum output current of 20 A each.

4. Does this module generate backup power?

No. It does not store or generate energy. It decouples two independent power supply branches so that one available supply can continue supporting the load if the other branch becomes unavailable, provided the remaining supply has sufficient capacity.

5. What is the difference between this model and 6EP1961-3BA21?

The 6AG1961-3BA21-7AX0 is a SIPLUS version based on the standard 6EP1961-3BA21. It includes conformal coating and has a specified operating temperature range of -40 to +70°C.

6. How is the module installed?

It snaps onto a DIN rail conforming to EN 60715, with a 35 × 7.5 mm or 35 × 15 mm profile. Input and output wiring uses screw terminals.

7. What do the green and red LEDs indicate?

The green LED indicates that both input voltages are above the configured switching threshold. The red LED indicates that at least one input voltage has fallen below that threshold.

8. Does the module provide a fault signal to a PLC?

Yes. It provides an isolated changeover relay contact for signaling. The contact can be connected to a suitable PLC input or monitoring circuit to report the status of the redundant supply inputs.

9. Can the module support a load greater than 40 A?

No. Its maximum aggregate output current is 40 A. The connected load and wiring must be designed within this limit, and the remaining supply must have sufficient capacity to support the required load during a power supply failure.

10. What should be checked before purchasing a replacement?

Verify the complete order number, base model, voltage and current ratings, temperature range, conformal coating, terminal arrangement, DIN rail mounting, and relay signaling functions. Also inspect the physical condition and confirm whether the unit is new, used, or refurbished.

Procurement and Maintenance Recommendations

When purchasing the Siemens 6AG1961-3BA21-7AX0, confirm the complete order number rather than relying only on the description “SIPLUS redundancy module.” The standard 6EP1961-3BA21 and SIPLUS 6AG1961-3BA21-7AX0 have related electrical functions but differ in environmental configuration.

For replacement projects, check the two power supply ratings, maximum load current, DC distribution design, switching threshold, and relay monitoring requirements. Ensure that the replacement can be installed on the existing DIN rail and that the terminal arrangement is compatible with the cabinet wiring.

For used or surplus units, inspect the housing, terminals, mounting clips, and visible electronic condition. Confirm that the status indicators and relay signaling function correctly during an appropriate test.

During routine maintenance, inspect terminal connections, verify output voltage, and check the condition of both power supply branches. Keep the control cabinet clean and maintain the required ventilation. Periodically verify that the connected load remains within the module’s rated current and that the remaining power supply can support critical equipment during a supply failure.

Conclusion

The Siemens 6AG1961-3BA21-7AX0 SIPLUS PS E202U Redundancy Module is designed to improve the availability of industrial 24 V DC power distribution systems. Based on the 6EP1961-3BA21 platform, it decouples two compatible SITOP power supplies and supports a rated output current of 40 A.

Its conformal-coated construction, wide operating temperature range, LED status indication, and isolated relay signaling make it suitable for demanding industrial automation installations. For reliable operation, engineers should verify the power supply configuration, total load current, installation conditions, and monitoring requirements before commissioning or replacement.