Product Overview

The Allen-Bradley 1756-PA75​ (catalog variants include 1756-PA75/B) is a 75-watt, universal-input AC power supply module designed exclusively for installation in Slot 0 (the leftmost dedicated power-supply slot) of Rockwell Automation ControlLogix® programmable automation controller (PAC) chassis—including the 1756-A4, A7, A10, A13, and A17. The primary function of the Allen-Bradley 1756-PA75​ is to convert facility-supplied alternating current (85–265 V AC, 47–63 Hz, auto-ranging) into the multiple regulated DC voltages required by the ControlLogix backplane: 5.1 V DC (up to 13 A), 3.3 V DC (up to 4 A), and 24 V DC (up to 2.8 A). These outputs power the chassis backplane electronics and all inserted modules—processor, communication cards, digital/analog I/O, motion modules, and specialty cards—eliminating the need for external DC power supplies for the logic portion of the system.The Allen-Bradley 1756-PA75​ is the most commonly specified standard-capacity ControlLogix power supply, offering sufficient backplane current budget for typical medium-density racks containing a ControlLogix processor (1756-L7x or L8x), one or two Ethernet/IP communication modules, and a moderate complement of local I/O modules. It features a hold-up time of ≥ 20 ms at full load (with 240 V AC input) to ride through brief mains interruptions, comprehensive electronic protection (overcurrent, overvoltage, short-circuit, and overtemperature with auto-recovery), and 250 V AC reinforced isolation between AC input and the DC backplane side. A front-panel green “PWR” LED indicates normal operation, while absence or flashing indicates a fault condition such as AC loss or overtemperature. The module is convection-cooled (no fan), operates from 0 °C to +60 °C, and can be paired with the 1756-PSCA2 (Power Supply Redundancy Cable Assembly) and a second Allen-Bradley 1756-PA75​ (or 1756-PB75) to create a 1+1 redundant power configuration for high-availability systems. Simple to install and fully recognized by the ControlLogix operating system without DIP-switch configuration, the Allen-Bradley 1756-PA75​ is the foundational power element of countless ControlLogix control cabinets worldwide.

Technical Specifications

Main Features and Advantages

The Allen-Bradley 1756-PA75​ delivers the core power infrastructure for ControlLogix systems with a focus on global deployability, reliability, and ease of integration.Worldwide AC input acceptance: The auto-ranging 85–265 V AC input means a single Allen-Bradley 1756-PA75​ part number can be shipped to—and installed in—plants anywhere in the world, whether the facility mains is 100 V AC (Japan), 120 V AC (North America), 208 V AC (industrial US), 230 V AC (Europe/Asia), or anywhere in between. No manual voltage selector or jumper change is required, reducing spare-parts complexity for multinational OEMs and end users.Multi-rail backplane power distribution: Rather than providing only a single output voltage, the Allen-Bradley 1756-PA75​ generates the three distinct regulated rails (5.1 V, 3.3 V, 24 V) needed by different generations and types of ControlLogix modules—older 5 V–dependent I/O, newer 3.3 V logic cores in L7x/L8x processors, and 24 V-referenced functions such as some analog module excitation or 1756-HSC high-speed counter inputs. This integrated approach keeps panel wiring clean and eliminates external DC supplies for backplane power.Brownout and transient ride-through: With a minimum 20 ms hold-up at full load (longer at partial load or 240 V input), the Allen-Bradley 1756-PA75​ sustains backplane voltage across brief mains sags or contactor drop-out events that are common in industrial power distributions, preventing spurious controller faults due to momentary AC flicker.Redundancy-ready architecture: Although a single Allen-Bradley 1756-PA75​ powers a standard rack, it can be deployed in a redundant pair using the 1756-PSCA2 redundancy cable and an optional 1756-PSPD (power supply distribution) mounting bracket or directly into two chassis slots in larger frames. This N+1 configuration ensures that a PSU failure does not interrupt controller operation—a key requirement in continuous-process, power-generation, and critical-infrastructure applications.Comprehensive self-protection & diagnostics: The module continuously monitors its own operating conditions. In the event of output overload, short, or excessive internal temperature, it shuts down the DC outputs in a controlled manner and attempts auto-restart when the fault clears. The front PWR LED extinguishes or flashes to alert maintenance staff; the condition is also reported to the controller as a power-supply status bit when the chassis contains a processor or is scanned by a supervisory controller via remote I/O.Passive, fanless construction: By relying on convection cooling through vented chassis side panels, the Allen-Bradley 1756-PA75​ introduces no acoustic noise and accumulates less dust than forced-air designs, contributing to longer service life in dusty or fibrous environments (always install inside a properly rated IP20 enclosure).

Application Field

The Allen-Bradley 1756-PA75​ is the default power supply chosen for the vast majority of standalone ControlLogix installations that draw their primary power from an AC mains source. In discrete manufacturing—automotive assembly lines, packaging machinery, bottling plants, and metal-stamping presses—it powers the ControlLogix processor (1756-L71/L72/L73/L75 or L81E/L82E/L83E/L85E), EtherNet/IP interface modules (1756-EN2T/EN3T/EN4T), digital and analog I/O modules for machine sensing and actuation, and motion control modules (1756-M08SE/M16SE) driving Kinetix servo drives, all from a single 1756-A7 or 1756-A10 chassis.In process automation—oil & gas, refining, chemical batching, pharmaceutical skids, and water/wastewater treatment—the Allen-Bradley 1756-PA75​ energizes ControlLogix controllers with ControlNet (1756-CN2R) or EtherNet/IP redundant communications, analog I/O for loop control (1756-IF8, 1756-OF8H), HART communication modules, and safety I/O (1756-IB16S/OB16S) in a single local rack. Where high availability is mandated, two Allen-Bradley 1756-PA75​ units are installed with redundancy cabling to form a fault-tolerant power subsystem.The module is also specified in material-handling control panels (airport baggage handling systems, warehouse AS/RS), building automation master controllers, and power-utility substation RTU/SCADA front-ends where 125 V DC is not the primary panel supply and an AC-powered, UL-listed, compact rack PSU is preferred. Its universal input range makes it equally suitable for OEM machinery exported internationally—one panel design, one Allen-Bradley 1756-PA75, any global mains voltage.