Application Scenarios
A packaging plant running a ControlLogix line on a 24V DC bus—common in facilities that have standardized on DC power for safety and battery-backup reasons—found its original AC-input supply incompatible with a planned power architecture upgrade. The maintenance team swapped in the 1756-PB75 to feed the chassis directly from the plant’s 24V DC distribution, eliminating a dedicated AC circuit and its associated transformer losses. When the facility’s DC bus experienced a brief voltage sag during a nearby motor start, the module’s 40 ms hold-up time at 24V kept the controller and I/O modules running without a single scan interruption . For plants already invested in DC infrastructure, the 1756-PB75 is the straightforward path to powering ControlLogix without adding AC conversion stages.
Parameter
| Main Parameters | Value/Description |
|---|---|
| Product Model | 1756-PB75 (Series A) |
| Manufacturer | Allen-Bradley (Rockwell Automation) |
| Product Category | ControlLogix Standard DC Power Supply |
| Input Voltage Range | 18–32V DC (24V DC nominal) |
| Maximum Output Power | 75W at 0–60°C |
| Backplane Outputs | 5.1V @ 13A; 3.3V @ 4A; 1.2V @ 1.5A; 24V @ 2.8A |
| Input Power (max) | 95W |
| Hold-Up Time | 35 ms @ 18V; 40 ms @ 24V; 40 ms @ 32V |
| Inrush Current (max) | 30A |
| Isolation | 250V continuous; type tested @ 3500V DC for 60s |
| Compatible Chassis | 1756-A4, A7, A10, A13, A17 (Series B and C) |
| Operating Temperature | 0°C to 60°C |
| Mounting Position | Leftmost slot of 1756 chassis |
The 13A available on the 5.1V rail is the figure to watch when populating a chassis—most ControlLogix modules draw primarily from this rail, and a rack full of communication and analog cards can approach the limit faster than expected . The 40 ms hold-up time provides a meaningful buffer against brief input interruptions, though it is not a substitute for a proper UPS on the 24V feed.
Technical Principles and Innovative Values
Innovation Point 1: Direct 24V DC Input for DC-Native Facilities. Many modern plants distribute 24V DC for control and safety systems, and the 1756-PB75 accepts that bus directly without an intermediate AC/DC stage. This eliminates a conversion loss, removes the need for a dedicated AC outlet inside the control cabinet, and simplifies compliance with DC-based safety architectures. The module’s 18–32V input range tolerates the voltage droop and recovery typical of battery-backed DC systems, so a sag during a transfer event does not drop the PLC.
Innovation Point 2: Reinforced Isolation Between Field and Backplane. The 1756-PB75 provides 250V continuous isolation from the 24V input to the backplane, type-tested at 3500V DC for 60 seconds . In practice, this means a fault or surge on the plant’s 24V distribution is blocked from propagating into the sensitive controller and I/O circuitry. For facilities where the DC bus runs alongside motor feeders or welders, that isolation layer is a meaningful reliability feature rather than a datasheet formality.
Innovation Point 3: Chassis-Left Mounting with No External Wiring. The module installs directly onto the left side of the chassis, mating with the backplane connector without any external cables. Input power lands on screw terminals rated for 2.5 mm² (14 AWG) copper wire. This integrated mounting means the supply is mechanically supported by the chassis itself, reducing strain on terminal connections and simplifying cabinet layout—there is no separate power supply enclosure or DIN-rail unit to accommodate .
