Allen-Bradley 1746-P7/A Power Supply Module

Configured for DC power conversion in SLC 500 chassis power distribution, the Allen-Bradley 1746-P7/A (1746-P7 Power Supply Module) provides direct electrical execution of regulated backplane and user supply rails across SLC 500 programmable controller platforms. The module converts 24 VDC input into isolated 5 VDC and 24 VDC outputs for processor and I/O subsystem energization.

Hardware Specifications

Backplane Power Regulation and Load Distribution

The module implements regulated DC conversion with dedicated internal current paths for 5 VDC logic rail and 24 VDC auxiliary rail. Backplane distribution is segmented to prevent cross-loading between logic and field supply domains. Internal regulation stages maintain output stability under variable inrush and transient conditions typical of SLC 500 chassis population changes.

Energization sequencing is tied to backplane enable signaling. During chassis insertion or module initialization, the power supply enforces controlled ramp behavior on the 5 VDC rail to limit processor reset instability. The 24 VDC auxiliary output is derived through isolated conversion stages to maintain separation from logic domain noise coupling.

Frequently Asked Questions

Q: Can the 1746-P7/A be hot-swapped while the SLC chassis is energized?
A: The module is not intended for live insertion under load conditions. Backplane voltage collapse during removal can induce CPU reset and I/O state transitions.

Q: What is the backplane current limitation at 5 VDC rail?
A: The internal current capacity supports up to 8 A at 5 VDC; exceeding chassis load budget may cause undervoltage on processor backplane supply.

Q: Does firmware or configuration affect power supply behavior?
A: No firmware layer exists in the module. Regulation behavior is hardware-defined and independent of CPU or rack configuration.

Field Installation Guidelines

Power input terminals shall be wired according to 24 VDC polarity requirements with controlled torque on screw terminals. Shielded conductors are not required for DC supply lines but routing should be separated from high-frequency switching conductors to reduce conducted noise coupling into backplane circuitry. Chassis grounding must be maintained through the SLC rack frame bonding point. Insertion must be performed with system power removed to avoid transient backplane voltage dips.