Allen-Bradley 1756-A17 ControlLogix Chassis

The Allen-Bradley 1756-A17, also cataloged as the 1756-A17 ControlLogix chassis, operates as a dedicated hardware component for modular backplane interconnection and power distribution within ControlLogix rack systems. Configured for 17-slot module accommodation, the 1756-A17 provides direct physical/electrical execution of backplane communication, enabling synchronized data exchange and power routing across installed PLC, I/O, and communication modules in a single chassis structure.

The chassis implements a shared ControlLogix backplane architecture with defined current distribution across 5.1 VDC and 24 VDC rails, supporting deterministic module-level coordination across all 17 slots.

Suffix Breakdown & Model Matrix

The model designation “1756-A17” defines a ControlLogix chassis series (1756), with “A17” indicating a 17-slot rack configuration. No additional functional suffix segmentation is defined by the manufacturer.

Hardware Specifications

ControlLogix Backplane Power and I/O Slot Distribution Behavior

Within the ControlLogix architecture, the 1756-A17 chassis provides a unified backplane bus where all 17 slots share deterministic electrical and communication pathways. The 5.1 VDC rail supports core logic and backplane signaling, while the 24 VDC rail distributes auxiliary module power. Slot-based current allocation is enforced to maintain stable backplane loading during mixed module configurations, including I/O, CPU, and communication cards.

The chassis design ensures mechanical stability through dual mounting tabs (top and bottom), maintaining alignment integrity under multi-module load conditions.

Frequently Asked Questions (FAQ)

Q: Does the 1756-A17 support hot-swapping of modules?
A: Yes. ControlLogix architecture supports hot-swapping. However, electrical transients on the backplane must be considered when inserting or removing high-load modules.

Q: Is backplane current isolated between slots?
A: No. The backplane is a shared electrical bus. Current is distributed across all slots within defined chassis and per-slot limits.

Q: Can all 17 slots be populated simultaneously at maximum load?
A: No. Total system loading must respect chassis-level current limits on 5.1 VDC and 24 VDC rails to avoid backplane overdraw.

Field Installation Guidelines

• Install chassis using both top and bottom mounting tabs to ensure mechanical stability

• Use approved Phillips or SEM screws with appropriate flat/star/split lock washers

• Maintain grounding continuity between chassis and cabinet earth bar before energization

• Verify backplane connector alignment prior to module insertion to avoid pin damage

• Distribute high-current modules across slots to prevent localized rail saturation

• Ensure adequate cabinet clearance for open-style chassis airflow and wiring access