ACS 800 encoder error #7301

Here at my job we have an ACS800 multidrive to control speed and torque of the hoist motor. This post is about the error code #7301 "encoder error" and the adventure it was trying to tackle it. This is done with the aim that some of the information here may be of good use to anyone dealing with this error.

First of all, if you are reading this in desperation because the encoder error trips your winder, here I have great news: you can change the error status from FAULT (default setting) to ALARM. It can be done using drive Windows software or through the keypad as well. Doing this will give you the extra time you need to perform troubleshooting without delaying / stopping operations. Off course, to take this decision you first have to evaluate it doesn't compromise safety of operations.

Here are the steps to follow when using Drive Windows:

1. Connect to drive.

2. Open parameters window. Go to parameter 50.

3. Double click on encoder. A little window will pop up where you can choose error status to be FAULT or ALARM. Click on ALARM then click OK and that's it.

Additionally, you may like to visit the following links since they may give you ideas about how to perform troubleshooting. It worked for me.

Link 1: ABB Forum
Link 2: Engineering tips

Now, this is my adventure with encoder error #7301...

This error has been showing up occasionally since the hoist commissioning (once per month as much) but lately it's been occurring more often (1 or 2 times per day) so we decided to allocate some time to check up the reason for this fault to occur.

Error 7301

According to the ACS800 troubleshooting, this error requires to check encoder wiring. Specifically the one attached to the motor's back since its signals go from the encoder to the AHC panel and then to the RTAC module at the drive control cabinet. 

So we did it, Wiring and connections were checked and tightened. We got a couple of days error free but then it started to show up again and -lucky we- it happened at peak hour. We changed the error status from FAULT to ALARM to give us chance to finish the shift and continue with troubleshooting.

Wiring check up at both ends and through cable tray

Next steps were made to determine which element was causing us headaches:

* Change encoder: no results.

* Change of Isolation amplifier card PE1315A at AHC: No results.

* Change of RTAC module: Error free for a week then it started again.

* Change encoder wiring from encoder to junction box: no results. Here we noticed that motor cover was deforming the wiring so we asked our mechanical people to modify it as a preventive measure despite it was not the cause of the fault.

* Change of encoder wiring from junction box to AHC panel: no results.

* Change of encoder wiring from AHC panel to RTAC module at drive: Eureka! We believe this wiring was damaged during installation.