Product Overview

The Allen-Bradley 1756-PBR2 is a high-reliability redundant power supply module designed for the ControlLogix platform. This unit provides a 24V DC power solution specifically engineered for mission-critical automation systems where continuous uptime is non-negotiable. By operating in a redundant pair with an identical module, the 1756-PBR2 ensures that the ControlLogix backplane remains energized even if a primary power source or an individual supply fails.

Unlike standard power supplies, the 1756-PBR2 is designed to mount externally to the ControlLogix chassis, connecting via a power adapter cable (such as the 1756-CPR2). This configuration allows for high-current delivery and improved thermal management, supporting large-scale processor, motion, and I/O configurations in demanding industrial environments.

Technical Specifications

• Manufacturer: Rockwell Automation / Allen-Bradley

• Model Number: 1756-PBR2

• Module Type: Redundant Power Supply (DC Input)

• Input Voltage Range: 18–32V DC (24V DC Nominal)

• Output Power: 13 A @ 1.2V DC; 13 A @ 3.3V DC; 10 A @ 5.1V DC; 2.8 A @ 24V DC

• Chassis Compatibility: ControlLogix 1756-A4, -A7, -A10, -A13, -A17

• Power Cable Requirement: 1756-CPR2 (sold separately)

• Operating Temperature: 0°C to 60°C (32°F to 140°F)

• Weight: 1.45 kg

• Dimensions: 14.2 x 17.5 x 13.2 cm

• Origin: USA

Key Technical Characteristics

• Automatic Fault Overaver: The module features an instantaneous, hardware-based failover mechanism. In a redundant setup, both supplies share the load; if one fails, the other immediately assumes the full load without causing a voltage dip on the backplane, preventing controller resets.

• Enhanced Diagnostics and Monitoring: Integrated status LEDs provide immediate visual feedback on "Power OK" and "Redundancy Ready" states. Furthermore, internal diagnostics can be monitored through the ControlLogix software, allowing for proactive maintenance before a total system failure occurs.

• Hot-Swap Capability: To maximize system availability, the 1756-PBR2 supports hot-swapping. Maintenance personnel can replace a faulty power module while the remaining unit continues to power the operational PLC rack.

• Industrial Hardening: Engineered for heavy industrial use, the unit is built to resist high levels of vibration and electromagnetic interference (EMI), ensuring stable DC output even in electrically noisy environments like power plants or refineries.

• Balanced Load Sharing: When both 1756-PBR2 units are healthy, they utilize active load-sharing circuitry to balance the current draw. This reduces the thermal stress on individual components and significantly extends the operational lifespan of the power system.

Primary Applications

The 1756-PBR2 is the standard choice for high-availability sectors, including:

• Oil & Gas: Critical control for offshore platforms and pipeline monitoring.

• Pharmaceutical: Continuous batch processing where power loss results in significant product waste.

• Power Generation: Reliable automation for turbine and balance-of-plant systems.

• Metals & Mining: Heavy-duty processing lines requiring high-vibration resistance.