1746-A4 | Allen-Bradley | SLC 500 Modular 4-Slot Backplane Chassis

Product Description

The 1746-A4 is a compact, 4-slot modular rack designed to serve as the physical and electrical backbone for the Allen-Bradley SLC 500 PLC platform. This chassis provides the necessary housing for a single power supply, one CPU (if used in the local rack), and a combination of I/O or specialty modules. Engineered for durability, the 1746-A4 (Part Number: 1746-A4) facilitates high-speed data communication across its integrated backplane, supporting both 5.1V DC and 24V DC power distribution to all installed components.

The frame is designed for secure panel mounting and features a dedicated grounding point to ensure system stability and electromagnetic interference (EMI) protection. For expanded control requirements, the 1746-A4 supports multi-chassis configurations via interconnecting cables, allowing up to three chassis to be linked to a single processor for a maximum of 30 slots. This makes it an ideal choice for localized control tasks or as a remote I/O drop in a larger distributed system.

Technical Specifications

• Manufacturer: Allen-Bradley / Rockwell Automation

• Model Number: 1746-A4

• Chassis Capacity: 4 Modular Slots

• Backplane Voltages: 5.1V DC and 24V DC

• Mounting Configuration: Panel Mount (Internal Cabinet)

• Expansion Limit: Up to 3 chassis total per system

• Interconnect Capability: Supports 1746-C7, 1746-C9, or 1746-C11 interconnect cables

• Grounding: Direct panel ground connection

• Chassis Weight: 0.60 kg (1.31 lbs)

• Dimensions: Approximately 17.1 x 19.5 x 14.5 cm

• System Compatibility: SLC 500 Series processors and 1746 I/O modules

Selection and Comparison

While the 1746-A4 is the smallest in the SLC 500 chassis family, it shares the same electrical specifications as the larger 1746-A7 (7-slot), 1746-A10 (10-slot), and 1746-A13 (13-slot) units. This 4-slot variant is specifically optimized for small-scale logic applications or space-constrained enclosures where high-density I/O is not immediately required but modularity remains a priority.

Engineering FAQ

Can I install the power supply in any slot of the 1746-A4?No, the power supply for the SLC 500 system must be mounted on the dedicated left-side power supply footprint of the 1746-A4. This footprint does not count toward the 4 available I/O slots.

What is the maximum distance between linked chassis?When using expansion cables to link a 1746-A4 to another rack, the total length of the interconnect cables must not exceed 30.48 cm (12 inches) for standard configurations to maintain signal integrity on the backplane bus.