Allen-Bradley 1756-PBR2 ControlLogix Redundant Power Supply Bundle Kit

Functional Summary

The 1756-PBR2 (1756PBR2) functions as a complete, factory-bundled redundant DC power solution within the Allen-Bradley ControlLogix automation framework. Engineered for high-availability process lifelines in critical infrastructure operations such as offshore drilling platforms, municipal water treatment facilities, and continuously operating steel manufacturing systems, this bundle eliminates power delivery single points of failure. By pairing two hardware-independent redundant power supplies with a specialized chassis adapter, the system achieves a fault-tolerant architecture. If one incoming power feed drops or an internal component fault occurs, the secondary power supply immediately maintains full backplane current requirements without shifting system voltage states, preventing expensive processor resets and reducing catastrophic facility downtime.

System Kit Components and Architecture

The 1756-PBR2 redundant bundle includes a matched set of industrial hardware components configured to form a synchronized power network:

• Two 1756-PB75R Redundant Power Supplies: These 24 VDC nominal power modules feature advanced internal decoupling diodes to safely manage load-sharing tasks and shield the backplane rail against upstream line short-circuits.

• One 1756-PSCA2 Chassis Adapter Module: This passive hardware module mounts directly to the left side of any standard 1756 ControlLogix chassis, serving as the localized connection plane that channels currents from both external supplies directly to the backplane pins.

• Two 1756-CPR2 Redundancy Cables: These heavy-duty, low-impedance connection links transfer DC output currents and critical status signaling from the independent power enclosures directly to the 1756-PSCA2 chassis adapter interface.

The integrated control electronics feature limited line hold-up capabilities to ride out temporary input voltage drops, alongside an early-warning shutdown broadcast loop that informs all local I/O and processor modules of an imminent voltage crash to ensure safe data persistence before power drops out completely.

Comprehensive Engineering Data

Frequently Asked Questions

Does the 1756-PBR2 bundle allow true live-swapping of an individual power module during operation?

Yes. Because the 1756-PBR2 bundle places the power supplies on an external mounting panel detached from the chassis, you can safely swap out a faulty 1756-PB75R module or disconnect its 1756-CPR2 cable under live operating conditions. The surviving power supply maintains the full load requirement, ensuring zero disruption to the active processor tasks.

Can the two 1756-PB75R units inside this bundle be powered from different 24 VDC source lines?

Yes, this is the recommended field design for maximizing infrastructure uptime. Wiring one supply module to a dedicated 24 VDC battery bank and the second module to an independent utility-driven 24 VDC industrial power source ensures continuous operation even during a complete plant utility blackout.

What is the specific purpose of the 1756-PSCA2 module included in this kit?

The 1756-PSCA2 is a passive routing adapter that occupies the standard left-hand power supply slot on a ControlLogix chassis. It contains no active internal conversion logic; instead, it provides the physical terminals for the two 1756-CPR2 redundancy cables, merging their independent output rails into a single backplane power feed.

Field Engineering and Installation Protocol

• Chassis Adapter Mechanical Fastening: Mount the 1756-PSCA2 adapter module securely onto the left-hand mounting pins of the standard ControlLogix chassis. Tighten the top and bottom captive hardware screws to lock the interface into place. Ensure the main chassis grounding lug uses a low-impedance copper strap tied directly to the enclosure ground bus bar to clear high-frequency noise from the incoming DC rails.

• Redundancy Cable Retention and Minimum Bend Radius: Connect the two 1756-CPR2 cables between the rear connectors of the 1756-PB75R supplies and the dual docking ports on the faceplate of the 1756-PSCA2 adapter. Secure all mechanical cable thumbscrews to protect against connection failure caused by field vibration. Do not bend the 1756-CPR2 cables past a minimum radius of 50 mm (2.0 inches) to prevent stress fatigue on the internal signaling strands.

• Thermal Management and Clearance Layout: External 1756-PB75R power units rely on natural convection to vent thermal energy. Mount the supplies vertically on a backpanel or DIN-rail structure, keeping at least 51 mm (2.0 inches) of clear space above and below each housing. Route all 24 VDC field power source lines in independent wire ways away from data links and high-voltage motor conductors to insulate the power network from inductive noise spikes.