Product Overview

The ABB TU845, identified by order reference 3BSE021447R1, is a specialized Module Termination Unit (MTU) engineered for high-availability configurations within the S800 I/O system. This unit acts as the physical and electrical interface between the field wiring and redundant I/O modules. By facilitating dual ModuleBus connections, the TU845 ensures that data integrity is maintained through hardware redundancy, making it a critical component for Distributed Control Systems (DCS) where process downtime is unacceptable. It supports 8-channel field signal interfacing and integrates built-in address logic, which automatically assigns positions to I/O modules to streamline network synchronization and system diagnostics.

Technical Configuration and Hardware Parameters

The TU845 3BSE021447R1 is designed for precision signal distribution and robust mechanical stability:

• I/O Channel Capacity: Supports 8 individual channels with 2+2 process voltage connections.

• Redundancy Interface: Dual ModuleBus connections for independent signal paths to redundant modules.

• Signal Flexibility: Compatible with TY801 shunt sticks for selectable voltage or current input monitoring.

• Electrical Ratings: Supports a maximum voltage of 50V and a continuous current of 2A per channel.

• Safety Mechanical Keying: Features 4 six-position keys (36 total combinations) to prevent the installation of incorrect module types.

• Chassis Dimensions: 18.5 x 13 x 6.2 cm.

• Net Weight: 0.58 kg.

• Mounting Protocol: DIN rail installation with an integrated grounding latch and mechanical lock.

• Manufacturing Origin: Sweden.

Specialized Industrial Deployments

The TU845 termination unit is optimized for mission-critical sectors requiring continuous 24/7 operation:

• Redundant Control Loops: Essential for safety-instrumented systems (SIS) and critical process control where signal failure would result in immediate system trips.

• Power Plant Automation: Managing high-density I/O signals in turbine control or auxiliary power systems that utilize redundant S800 I/O modules.

• Complex Network Routing: Facilitating the seamless shifting of address signals across the ModuleBus for large-scale automation racks.

• Field Power Distribution: Providing 2-wire field connections and centralized process power distribution to reduce wiring complexity in industrial control cabinets.

FAQ

Q: What is the primary function of the redundancy feature in the TU845?

A: The TU845 allows two identical I/O modules to be connected simultaneously. If one module fails, the system automatically continues operation through the second module via the redundant ModuleBus paths provided by the termination unit.

Q: How does the TU845 ensure that I do not plug in the wrong I/O module?

A: The unit is equipped with a mechanical keying system consisting of four keys, each with six positions. This allows for 36 different configurations, ensuring only the specifically assigned module type can be physically inserted.

Q: Is it possible to use both current and voltage signals on the same TU845 unit?

A: Yes, the unit utilizes TY801 individual shunt sticks for each channel. By choosing the appropriate shunt, you can configure individual channels for either voltage or current inputs based on field device requirements.

Q: Does the TU845 3BSE021447R1 require a separate ground connection?

A: The unit features a mechanical latch that firmly attaches it to the DIN rail. This latching device doubles as a grounding mechanism to ensure the MTU is correctly bonded to the system ground through the rail.

Q: Can this unit be used with a single (non-redundant) ModuleBus?

A: While the TU845 is specifically designed for redundancy with two ModuleBus connections, it can operate in a single-bus environment; however, its primary value is realized in high-availability redundant architectures.