Product Overview

The Allen-Bradley 1756-PB75 is a high-performance DC-to-DC power supply module engineered to provide the primary backplane power for any ControlLogix® 1756 chassis. Designed for systems operating on a nominal 24V DC input, this unit converts raw industrial power into the precisely regulated voltages required by processors, communication adapters, and I/O modules. With a robust 75-watt capacity, it is the standard choice for remote I/O racks and local controller chassis in environments where AC power is unavailable or DC battery backup is prioritized.

The 1756-PB75 is built for mission-critical reliability. It features a high hold-up time of 35 to 40 milliseconds, which allows the system to bridge momentary voltage drops without triggering a processor fault or system reset. This "ride-through" capability is essential for maintain system uptime in facilities with heavy motor starting or unstable DC grids. The module mounts securely to the leftmost side of the chassis, physically interlocking with the backplane to ensure a vibration-resistant connection.

Technical Architecture and Safety

Safety and signal integrity are central to the 1756-PB75 design. It utilizes reinforced insulation to provide a high level of isolation between the input power source and the sensitive logic circuits on the backplane. This protects the PLC hardware from field-side electrical noise and surges.

• Input Versatility: While optimized for 24V DC, the module maintains full regulation across a broad input window of 18V to 32V DC, accommodating battery discharge curves and charging fluctuations.

• Dual Voltage Rail Output: Efficiently distributes 13A at 5.1V DC for logic processing and 2.8A at 24V DC for module-specific requirements.

• Overcurrent Protection: Integrated non-user-replaceable fusing and internal thermal shutdown mechanisms prevent damage during short circuits or overheating.

• Status Monitoring: A front-panel green LED provides immediate visual confirmation that the supply is within the operational output range.

Technical Specifications

• Manufacturer: Allen-Bradley (Rockwell Automation)

• Model Number: 1756-PB75

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

• Power Output: 75 Watts @ 60°C

• Backplane Current (Max): 13A @ 5.1V DC and 2.8A @ 24V DC

• Input Current (Max): 4.3A @ 18V DC; 3.2A @ 24V DC

• Inrush Current: 30A (Maximum)

• Isolation Voltage: 250V (Continuous), tested at 3500V DC for 60 seconds

• Wiring Gauge: 2.5 mm² (14 AWG) Solid or Stranded Copper

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

• Dimensions: 14.5 x 3.5 x 13.0 cm

• Weight: 0.9 kg (2.1 lbs)

Installation and Environmental Resistance

• Chassis Compatibility: Specifically designed for all standard 1756 ControlLogix chassis, including A4, A7, A10, A13, and A17 models.

• Thermal Management: The housing is optimized for convection cooling, allowing it to maintain a 75W output even at the maximum operating temperature of 60°C without the need for external fans.

• Mechanical Durability: Rated for industrial-grade shock and vibration, ensuring it remains operational in high-motion environments or when mounted on machinery.

• Compliance: Meets global standards including UL, CSA, CE, and C-TICK for use in diverse industrial sectors.