Product Overview

The Allen-Bradley 1756-PB75R is a high-availability DC redundant power supply engineered for the ControlLogix® platform. Designed for mission-critical automation systems, this 75-watt module ensures continuous operation by allowing two power supplies to share the chassis load. In the event of a single supply failure, the 1756-PB75R manages an instantaneous and seamless transition, preventing controller resets and avoiding costly system downtime.

Operating on a nominal 24V DC input, the 1756-PB75R provides regulated power across the backplane to support a variety of I/O, processors, and communication modules. Its robust design is particularly suited for industries where process continuity is paramount, such as oil and gas, power generation, and pharmaceutical manufacturing.

High-Availability Features and System Logic

The 1756-PB75R is built with specific hardware logic to maintain system integrity during electrical fluctuations.

• Active Load Sharing: When paired in a redundant configuration, two modules automatically balance the current draw, which reduces thermal stress on individual components and extends the lifespan of the hardware.

• Integrated Diagnostics: Features a front-panel status indicator and a built-in solid-state relay (annunciator) that can be wired to an input module to provide real-time alerts to the controller if power redundancy is lost.

• Superior Ride-Through: Provides a 20-millisecond hold-up time, allowing the PLC to remain operational during brief voltage dips or power switching transients.

• Hazardous Location Certified: Built to meet ATEX and IECEx standards, making it suitable for deployment in explosive atmospheres where safety compliance is a strict requirement.

• Chassis Flexibility: Fully compatible with standard 1756-A4, A7, A10, A13, and A17 chassis through the use of the 1756-PSCA2 redundant power supply adapter.

Technical Specifications

• Manufacturer: Allen-Bradley (Rockwell Automation)

• Model Number: 1756-PB75R

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

• Output Power: 75 Watts @ 60°C

• Inrush Current: 30 Amperes (Maximum)

• Hold-up Time: 20 ms @ 24V DC

• Isolation Voltage: 250V (Continuous); Tested at 3250V DC for 60 seconds

• Annunciator Power: 24V DC or 90V DC (Standard/Hazardous ratings)

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

• Dimensions: 14.1 x 17.4 x 13.6 cm

• Weight: 1.46 kg (3.2 lbs)

Installation and Safety Requirements

To implement a fully redundant power solution, the 1756-PB75R requires the 1756-CPR2 redundancy cable to link the supply to the 1756-PSCA2 chassis adapter. This physical separation of the power supply from the chassis allows for better heat management and simplified maintenance.

Safety Note: While the system supports redundancy, the 1756-CPR2 cable must not be connected or disconnected while power is applied in hazardous environments to prevent electrical arcing. The module features 15g operational shock resistance and 2g vibration tolerance, ensuring it remains reliable in heavy industrial environments.