ABB OTAC Series Modules

Technical Dossier

Product Details And Specifications

ABB OTAC Series: Comprehensive Module Range and Technical Overview

The ABB OTAC series comprises pulse encoder interface modules designed for integration with ABB AC drives — primarily the ACS 600, ACS 800, and ACS 1000 drive families. These modules serve as the critical feedback link between incremental rotary encoders and the drive's speed/position control loop, enabling closed-loop vector control in high-demand industrial applications.

OTAC modules are deployed across global heavy industry sectors including petrochemical refineries, nuclear power auxiliary systems, offshore platform drives, pulp and paper mills, and steel rolling lines. Their role in precision speed regulation makes them a long-term maintenance item: a single failed encoder interface module can halt an entire production line. As a result, maintaining a verified spare parts inventory of OTAC modules is standard practice in facilities with ABB drive installations.

The Evolution of OTAC Series Architecture

The OTAC designation was introduced by ABB as part of the option board ecosystem for the RDCO/RDNA communication and I/O expansion framework used across the ACS 600 and ACS 800 drive platforms. Early OTAC variants supported single-ended TTL encoder signals with fixed pulse count ranges. Subsequent revisions introduced differential signal support (RS-422), extended pulse frequency handling, and compatibility with the RMIO-02 and RMIO-11 main control boards.

As ABB transitioned its drive portfolio toward the ACS880 and ACS580 platforms, encoder feedback was increasingly handled by the FSE-31 and FEN-31 encoder interface modules — the functional successors to the OTAC line. However, the installed base of ACS 600 and ACS 800 drives remains substantial globally, and OTAC modules continue to be required for maintenance and emergency replacement well into the 2020s. The series is now in its end-of-life phase, with ABB no longer manufacturing new units, making verified aftermarket and refurbished stock the primary sourcing channel.

OTAC Series Full Catalog & Functionalities (SKU List)

The following SKUs represent the documented OTAC series range. Each module is classified by its primary function within the ABB drive option board architecture:

Pulse Encoder Interface Modules (Speed/Position Feedback)

• OTAC-01: Standard TTL pulse encoder interface for ACS 600/800; supports incremental encoders up to 65535 ppr
• OTAC-02: Differential RS-422 encoder interface; enhanced noise immunity for long cable runs in industrial environments
• OTAC-03: High-frequency encoder interface variant; supports pulse frequencies up to 500 kHz for high-speed spindle applications
• OTAC-11: Extended temperature range encoder interface; rated for ambient operation in harsh environments
• OTAC-21: Dual-channel encoder interface; supports simultaneous master/follower encoder feedback configurations

Associated Option Boards & Compatible Modules (ACS 600 / ACS 800 Platform)

• RTAC-01: Pulse encoder interface for ACS 600 standard drive; direct OTAC functional equivalent on earlier hardware revision
• RTAC-02: Differential encoder interface for ACS 600; RS-422 signal standard
• RDIO-01: Digital I/O extension module; 4DI / 2DO; mounts on RMIO control board
• RDIO-02: Digital I/O extension module; 4DI / 2DO with relay outputs
• RAIO-01: Analog I/O extension module; 2AI / 2AO; ±10V / 0–20mA configurable
• RAIO-02: Analog I/O extension module with isolated channels; for process control applications
• RDCO-01: DDCS fiber optic communication module; connects drive to ACS 600 master follower chain
• RDCO-02: DDCS fiber optic module; extended channel configuration for multi-drive systems
• RDCO-04: DDCS fiber optic module; 4-channel variant for large drive network topologies
• RMIO-02: Main control board for ACS 800 standard drive; primary host board for OTAC option modules
• RMIO-11: Main control board for ACS 800 with extended I/O; compatible with OTAC-01 and OTAC-02
• RINT-5611C: Rectifier control board for ACS 800 supply unit; associated control hardware in multi-drive configurations
• AINT-02C: Auxiliary inverter control board; used in ACS 800 multi-drive cabinet configurations
• APBU-44C: Branching unit for DDCS fiber optic network; connects multiple drives to a single master controller

Sourcing Hard-to-Find & Obsolete OTAC Series Parts

ABB has formally discontinued production of OTAC series modules. Standard ABB distribution channels no longer carry new stock. For facilities operating ACS 600 or ACS 800 drives, the available sourcing options are: certified refurbished units from specialist industrial electronics suppliers, new-old-stock (NOS) from decommissioned plant equipment, and tested pull-out units from drive repair centers.

DriveKNMS maintains a dedicated inventory of OTAC series modules sourced from verified industrial decommissioning projects and authorized repair facilities. Each unit is cataloged by hardware revision and firmware compatibility. For critical applications, we recommend sourcing a minimum of two spare OTAC modules per drive installation to cover both scheduled maintenance and unplanned failure events. Inquiries for bulk quantities, specific hardware revisions, or time-critical emergency orders are handled directly by our technical sales team.

Quality Control for the OTAC Series Range

OTAC modules interface directly with the drive's main control board via a proprietary option slot connector. Failure modes include corrupted encoder signal output, intermittent communication faults logged as encoder feedback errors (fault codes F-28, F-29 on ACS 800), and complete module non-response due to connector pin oxidation or internal component degradation.

DriveKNMS applies the following test protocol to all OTAC units prior to dispatch: visual inspection of the option slot connector for pin deformation and oxidation; functional bench test using an ACS 800 test rig with a calibrated incremental encoder signal source; verification of pulse count accuracy across the full ppr range; signal integrity measurement on both TTL and RS-422 output channels; and a 24-hour burn-in cycle under simulated load conditions. Units that do not pass all stages are quarantined and not offered for sale.