Description

The TU844 (Part Number: 3BSE021445R1) is a specialized Redundant Module Termination Unit (MTU) manufactured by ABB. Designed for the S800 and AC 800M I/O systems, this unit serves as the physical foundation for high-availability automation setups. Unlike standard bases that hold a single module, the TU844 is engineered to mount two I/O modules side-by-side (e.g., two AI810 or AO810 modules). It provides the necessary wiring interface and internal bus connections to support redundant configurations, ensuring that if one module fails, the second takes over instantly without disrupting the process.

Application Scenarios

Consider a nuclear power plant where the cooling system’s temperature must be monitored 24/7 without fail. A single point of failure in the control system is unacceptable. In this scenario, the TU844 is installed in the main control cabinet, holding two AI810 analog input modules. Both modules read the same temperature sensor data simultaneously. If the primary module malfunctions due to an internal electronic fault, the system seamlessly switches to the secondary module connected via the TU844. This redundancy ensures that the safety system remains active, preventing a potential meltdown. The TU844 effectively acts as the “insurance policy” for the physical wiring and module connection.