Description

The ABB TB853 is a specialized Termination Base designed exclusively for Redundant Control Links (RCU) within the ABB AC 800M controller family. Serving as the crucial interface between the controller’s communication ports and the fieldbus cabling (typically Profibus DP or ABB proprietary links), the TB853 ensures signal integrity in high-speed, dual-channel networks. Its defining feature is the built-in Terminal Resistance (usually selectable or fixed at 120Ω), which is mandatory for terminating the ends of a bus segment to eliminate signal reflections that lead to communication errors. Engineered for maximum availability, the TB853 supports hot-swapping of connected modules without disrupting the process, features superior EMC shielding connections, and provides a secure, screw-terminal block for robust wiring in harsh industrial environments. It is the backbone of reliable redundancy in critical automation architectures.

Application Scenarios

In a large petrochemical refinery, the Emergency Shutdown (ESD) system relied on an ABB AC 800M High Integrity (HI) configuration with redundant controllers communicating over a Profibus DP network. During a routine inspection, technicians discovered corrosion on an old termination unit, causing intermittent “Bus Fault” alarms and risking a loss of redundancy. The engineering team replaced the degraded unit with a new ABB TB853. The integrated terminal resistance of the TB853 immediately stabilized the bus impedance, clearing the communication errors. The robust shielding ground of the new base also filtered out electrical noise from nearby variable frequency drives. This simple replacement restored full redundant capability to the ESD system, ensuring the plant could safely handle any future fault conditions without unplanned downtime.