ABB RTAC-01 Pulse Encoder Interface Module for ACS800

ABB RTAC-01 pulse encoder interface

The ABB RTAC-01 is a pulse encoder interface module for ABB ACS800 drives. It feeds incremental encoder signals into the drive’s speed measurement so that speed control is accurate even at low speed.

It is a legacy module and is requested mainly for maintaining existing ACS800 systems.

On an ACS800, the module is wired to the incremental encoder and set up with the drive’s encoder parameters, for example pulses per revolution and encoder supply selection. Closed-loop speed control gives a steadier speed than sensorless operation, especially near zero speed and under changing load.

Technical specifications

Signal and wiring data

The module accepts signals up to 200 kHz and delivers a speed feedback resolution of 15 bit. It supplies the encoder with 24 V or 15 V at up to 5 W, short-circuit proof. The 300, 200 and 100 m cable limits depend on the encoder output type. A rotary switch sets the node ID between 16 and 31, and the 38-pin connector joins the module to the drive.

Use shielded twisted-pair cable, keep it away from motor cables, and choose the supply voltage that matches the encoder. A wrong supply setting can damage the encoder, so check the encoder datasheet. The module carries a short-circuit proof supply, but a wiring fault will still stop speed feedback and trip the drive.

Compatibility and order code

RTAC is ABB’s pulse encoder interface family and 01 the version. ABB states compatibility with the ACS800 Standard Application Program ASXR7000 or later. It is not listed for the ACS880; for that series use the ACS880-01 option list and modules such as the FEN-31. See encoders for related items.

The ASXR7000 program requirement is the main compatibility check. If your drive uses another application program, read the program’s own firmware manual before choosing this interface, and confirm the encoder pulse count your motor shaft needs.

Please include the planned installation altitude, the ambient temperature range and the type of enclosure or cabinet in your request, so that derating and cooling can be checked against the manufacturer’s data before a quotation is issued.

An option module is only useful when it matches both the drive and the network, so send us the drive type code, its firmware level and the controller that will talk to it. Add the required cable length and connector type. With those facts the right module can be confirmed, and the manual attached here helps your engineer check the parameters.

When an ACS800 needs encoder feedback

Many ACS800 drives run perfectly well without an encoder, but some applications depend on accurate speed or position information that sensorless control cannot provide on its own. Typical cases are machines that must hold speed close to zero, drives that start against a heavy load, hoisting and winding duties, and processes where several drives must keep a fixed speed relationship. In these applications the RTAC-01 provides the link between the incremental encoder on the motor shaft and the speed measurement inside the drive. When an existing ACS800 installation was commissioned with encoder feedback, the drive parameters, the control strategy and often the safety logic of the machine have been set up around that feedback, so a faulty interface module is usually replaced like for like rather than redesigning the control.

Selection guidance for a replacement module

The first check is the drive itself: confirm that it is an ACS800 running the Standard Application Program ASXR7000 or later, as stated by ABB. Next, look at the encoder. Note its output type and its supply voltage from the encoder nameplate or data sheet, because the RTAC-01 offers either 24 V or 15 V supply and the permissible cable length depends on the encoder output type. Measure or estimate the actual cable run between the encoder and the drive and compare it with the limits in the specification table. Finally, check the pulse count of the encoder against the maximum pulse frequency at the highest motor speed the application uses. If all of these points agree, the RTAC-01 is the right module; if the drive is an ACS880, the page above points to the separate option list for that series.

Installation and commissioning considerations

Before removing an old module, record its node ID switch position and photograph the wiring, so that the new module can be set and connected in exactly the same way. Isolate the drive and observe the waiting time given in the ABB drive manual before touching any part of it. Fit the module, set the node ID, and reconnect the encoder cable with the shield terminated as the manual describes. Before running the motor, check the encoder parameters in the drive, particularly the pulses per revolution and the supply selection. A first run at low speed, watching the measured speed against the reference and checking the direction of rotation, will show quickly whether the feedback is correct before the drive is returned to full duty.

How to specify your RFQ

Send the type code RTAC-01, the quantity and the delivery point, together with the full type code of the ACS800 drive and its application program. Add the encoder make and type, its supply voltage and output type, and the cable length. If you are replacing a failed module, a photo of the old module label and of the drive rating plate helps us confirm the match before we quote.

Documents and quotation

The attached ABB manual (3AFE64486853) gives wiring, jumper and parameter settings.

Please confirm before ordering: the drive type and firmware, the option slot, the network scanner or PLC and the cable type. Seven Star LLC is an independent supplier in Muscat and confirms current availability and lead time when it quotes.