Product Overview

The Allen-Bradley 1794-TB3K is a specialized terminal base unit designed for the FLEX I/O platform, serving as the essential mounting and wiring backbone for individual I/O modules. This unit facilitates the electrical connection between field sensors/actuators and the FLEXbus communication backplane. A critical feature of the "K" variant is its factory-applied conformal coating, which provides an added layer of protection against moisture, dust, and corrosive chemical environments, making it ideal for harsh industrial applications.

The 1794-TB3K utilizes a 3-wire termination style, offering a high-density connection point that simplifies cabinet layout by providing integrated power and common terminals for each I/O point. This design eliminates the need for external terminal strips for many applications, reducing overall installation time and panel space requirements. By angling the unit onto a standard DIN rail and engaging the locking mechanism, users create a rigid foundation that supports hot-swapping of I/O modules without disturbing the field wiring.

Electrical and Mechanical Interface

This terminal base is engineered for versatility, supporting a wide voltage range up to 125V AC/DC. The wiring architecture consists of 16 dedicated I/O terminals, 18 common terminals, and 18 voltage terminals. This generous allocation of termination points allows for efficient daisy-chaining of field power to adjacent terminal bases, streamlining the power distribution network within the I/O rack.

The unit features robust screw-clamp terminals designed to accept wire sizes from 24 to 16 AWG. To ensure long-term electrical stability in high-vibration environments, the terminals are rated for a specific torque range of 0.56–0.79 Nm. Furthermore, the 1794-TB3K provides complete galvanic isolation between the field-side wiring and the logic-side FLEXbus, protecting the central PLC processor from field-induced electrical noise or surges.

Technical Specifications

• Manufacturer: Allen-Bradley (Rockwell Automation)

• Model Number: 1794-TB3K

• Product Type: Terminal Base Unit

• Environmental Protection: Conformal Coated (K-Version)

• Maximum Voltage: 125V AC/DC

• Current Capacity: 10A Maximum

• Termination Count: 16 I/O, 18 Common, 18 Voltage terminals

• Wire Gauge Compatibility: 24–16 AWG stranded copper

• Terminal Torque: 0.56–0.79 Nm (5–7 lb-in)

• Operating Temperature: -20°C to +70°C (-4°F to +158°F)

• Shock/Vibration: 30G Functional Shock; 5G Vibration

• Physical Dimensions: 9  x 9  x 7 cm (Standard FLEX footprint)

• Certifications: c-UL-us, UL, CSA, CE, Ex, Marine

• Manufacturing Origin: USA

Industrial Reliability and Mounting

• Ruggedized Design: Conformal coating ensures reliable operation in "Class G3" harsh environments, preventing dendritic growth and silver corrosion.

• DIN Rail Integration: Supports rapid assembly on standard 35mm DIN rails with integrated grounding and interlocking tabs for adjacent units.

• Simplified Power Distribution: Dedicated voltage and common buses reduce the complexity of wiring auxiliary power to field devices.

• Serviceability: Allows for "Removal and Insertion Under Power" (RIUP), enabling module replacement while the rest of the FLEX I/O system remains operational.