Allen Bradley 1769-PA2 CompactLogix Power Supply Module

Allen Bradley 1769-PA2 Compact I/O Power Supply

Configured for high-efficiency DC power distribution in Allen Bradley industrial control architectures, the Allen Bradley 1769-PA2, also cataloged as the 1769-PA2 Compact I/O Power Supply, provides direct physical/electrical execution. It regulates high-voltage AC input into clean backplane power to drive local and distributed I/O chassis configurations without reliance on secondary transformers.

Hardware Specifications

Industrial Control Backplane Dynamics

The 1769-PA2 establishes a rigid backplane bus communication velocity framework by maintaining consistent power rails under high-density loads. Because local CompactLogix architectures depend on deterministic networks like EtherNet/IP for real-time operations, this power module isolates internal digital logic circuitry from line spikes. The 1500 V RMS galvanic isolation protects the microprocessors from common-mode electrical noise. Furthermore, the unit supports structured I/O density scaling by maintaining steady voltage rails across the interconnecting bus connectors, preventing voltage sags that can corrupt firmware flash compatibility during controller runtime executions.

Frequently Asked Questions

Q: Can the 1769-PA2 power supply be used in a hot-swap configuration while the system is powered?

A: No. The 1769-PA2 does not support hot-swap capabilities. You must completely disconnect the AC main input line power before inserting or extracting the power supply or any adjacent 1769 expansion modules to avoid backplane arcing and permanent processor fault cycles.

Q: How does the module handle systems that exceed the 8-module expansion limit?

A: The physical backplane current limits allow a maximum of 8 I/O modules per power supply bank. If your configuration requires more than 8 modules, you must insert an additional 1769-PA2 or compatible expansion power supply into the next bank via a bus expansion cable to balance the electrical load.

Q: What happens if the inrush current spikes to the maximum 25 A rating during power-up?

A: The internal power circuits are rated to withstand a 25 A peak inrush current for a fraction of a cycle at 264 VAC. This behavior is standard for capacitive charging circuits. Ensure your upstream circuit breakers or branch fuses are sized appropriately with time-delay curves to prevent nuisance tripping during initialization.

Field Installation Guidelines

• Chassis Ground Routing: Always run a low-impedance copper grounding wire from the functional earth (FE) terminal on the module directly to a centralized copper ground bus block. Do not daisy-chain the ground connection through multiple chassis parts.
• DIN-Rail Stability Lock: When mounting the hardware on a 35 mm DIN rail, engage the integrated locking mechanism firmly. Install mechanical end anchors on both ends of the completed module stack to prevent lateral movement and intermittent contact across the backplane bus pins.
• Thermal Venting Clearance: Maintain at least 50 mm (2 inches) of free space above, below, and to the sides of the module housing. This gap is necessary to ensure natural convection cooling draws heat away from the internal transformer elements.
• Wiring Separation Practices: Route high-voltage AC input lines through a separate conduit away from low-voltage DC signals and communication cables. This separate path minimizes electromagnetic interference across your signal loops.