Product Overview

The Allen-Bradley 1756-PB50 is a highly reliable DC-input power supply unit specifically designed for the ControlLogix architecture. Engineered to deliver stable, high-performance power to the chassis backplane, this unit is essential for maintaining the operational integrity of complex automation systems in demanding industrial environments. As a standard DC power supply, the 1756-PB50 accepts a nominal input of 24V DC (range: 18–32V DC) and provides a total power output of 60W, ensuring consistent energy delivery to I/O modules, communication bridges, and processor controllers installed within the chassis.

Unlike standard I/O modules, the 1756-PB50 is engineered for a unique installation position: it mounts directly to the leftmost side of any 1756 ControlLogix chassis, effectively serving as the backbone of the rack’s electrical infrastructure. Its advanced features, including "Hold-Up" time capability, protect the system from transient voltage drops, ensuring that control logic remains active even during minor power fluctuations. With ruggedized construction and compliance with rigorous vibration and thermal standards, this power supply is the gold standard for decentralized process plants, automotive manufacturing lines, and aerospace assembly stations where downtime is not an option.

Technical Specifications

Model Configuration Explanation

The 1756-PB50 designation provides a precise roadmap for system integration:

• 1756: Identifies the ControlLogix system hardware family.

• P: Designates the module as a Power Supply.

• B: Specifies the input type, with 'B' representing DC power (24V DC).

• 50: Denotes the power tier/capacity rating (50 series classification), ensuring engineers match the module to the total power budget of the chassis.

Typical Applications

• Automotive & Aerospace: Powers centralized assembly stations, robotics, and safety-rated motion control systems.

• Food & Beverage: Ideal for stainless steel, temperature-controlled panels requiring decentralized process control.

• Water & Wastewater Treatment: Provides reliable power to remote, decentralized I/O chassis in outdoor or harsh process environments.

• Heavy Machinery: Supports complex ControlLogix racks used in packaging, material handling, and high-speed sorting applications.

System Compatibility

The 1756-PB50 is fully compatible with the entire range of ControlLogix chassis, including 1756-A4, 1756-A7, 1756-A10, 1756-A13, and 1756-A17 (Series A, B, and C). It is designed to power any combination of I/O, communication, and specialty modules within these racks. Because it occupies the leftmost position of the chassis (outside the standard module slot numbering), it does not compete for space with PLC or communication cards, allowing for maximum rack utilization.

Installation Guidelines

• Mounting Protocol: Align the power supply circuit board with the card guides located on the far left side of the chassis. Slide the module back until it is fully flush with the front of the chassis.

• Terminal Connections: Connect the positive DC lead to Terminal 1 (DC+) and the negative lead to Terminal 2 (DC-). Terminal 3 remains unused.

• Wiring Standards: Utilize 14 AWG (2.5 mm²) solid or stranded copper wire rated for 90°C (194°F) or higher. Ensure insulation thickness does not exceed 1.2 mm.

• Cable Retention: Utilize the integrated V-groove on the front of the supply to route the power cable, and secure it with a cable tie to prevent strain on the terminals.

• Environment: Ensure the unit is installed in an environment with adequate airflow, adhering to the 0-60°C temperature range.

Product Advantages

• Hold-Up Time: Offers significant protection against power grid instability; the unit maintains operations for 30–40 ms during voltage dips.

• Isolation Excellence: Provides 250V continuous isolation, ensuring that backplane logic is shielded from external power noise.

• Maximum Rack Density: Its unique external left-side mounting preserves precious rack space, allowing more modules to be installed per chassis.

• Scalable Compatibility: Works across all major ControlLogix chassis series (A, B, C), making it a versatile choice for both legacy system maintenance and new installations.

Ordering Information

• 1756-PB50 DC ControlLogix Power Supply module.

• Note: This unit does not come with mounting screws or cable ties; check chassis documentation for necessary hardware. Order spare terminal blocks separately if needed for field maintenance.

Frequently Asked Questions

• Does the 1756-PB50 take up a module slot in the chassis?

  No. The power supply mounts to the extreme left of the chassis, effectively leaving all standard module slots open for your CPU and I/O cards.

• What happens if the input voltage drops below 18V DC?

  The module may cease operation. However, the internal "Hold-Up" time feature provides enough energy to maintain system stability for a short duration during minor dips.

• Can I use this power supply with an AC-powered chassis?

  No. This is a dedicated DC (18-32V) input module. Attempting to connect AC voltage will cause permanent damage. Use the 1756-PA series for AC requirements.

• What does the "Series A, B, C" compatibility mean?

  It signifies the module is designed to fit and function within various generations of ControlLogix chassis architectures, ensuring long-term support for your equipment.

• Why is there a difference in output power at 50°C vs 60°C?

  Industrial electronics undergo thermal derating. At higher temperatures (60°C), the power supply must reduce its output wattage (50W) to prevent component overheating.

• Is the 1756-PB50 suitable for redundant power configurations?

  Yes, you can install a second power supply on the far right of the chassis for redundancy, provided you have a chassis designed to support dual power supplies.

• How do I know if the power supply is failing?

  Monitor the LED indicators on the front panel. A loss of power or flashing status often indicates a fault or an input voltage that is out of the required range.

• Can I use this supply to power 24V field devices?

  While it provides 24V DC to the chassis backplane for modules, you should not exceed the current capacity limits (2.5A) if drawing power for external field devices.