Allen-Bradley 1756-PH75 ControlLogix 125V DC Power Supply

Description

The 1756-PH75 is a ControlLogix power supply manufactured by Allen-Bradley (Rockwell Automation), designed to accept a nominal 125V DC input and provide regulated power to the 1756 chassis backplane. It delivers up to 75 watts of total output across the 1.2V, 3.3V, 5.1V, and 24V backplane rails, supporting the full range of ControlLogix I/O and communication modules in standard chassis configurations.

Application Scenarios

A substation automation retrofit project requires a ControlLogix control system to operate from a station battery bank rather than a conventional AC supply. The existing 1756 chassis is populated with analog input modules for transformer monitoring and digital output modules for breaker control, but the original AC power supply cannot be connected to the DC station bus. The 1756-PH75 addresses this by accepting the station battery’s 125V DC nominal voltage directly—within its 90 to 143 VDC operating range—and converting it to the multiple backplane voltages that the ControlLogix modules require . Because the 1756-PH75 is a standard-width power supply, it occupies the leftmost slot of the chassis without requiring a separate external DC-to-AC inverter or a dedicated AC feed into the switchgear room. The retrofit team installs the 1756-PH75, verifies the 5.1V rail’s 13-amp capacity against the chassis’s module load calculation, and commissions the system on station battery power—eliminating a potential single point of failure tied to AC auxiliary supply availability.

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