The F0023 alarm code on your ABB ACS550 drive confirms an encoder error. This means the drive isn't receiving a proper signal from the motor's encoder, hindering its ability to precisely control motor speed and position.

This fault indicate that the drive is not detecting a valid encoder signal.

Check for and correct:

1. Encoder presence and proper connection (reverse wired = channel A connected to terminal of channel B or vice versa, loose connection or short circuit).
2. Voltage logic levels are outside of the specified range.
3. A working and properly connected Pulse Encoder Interface Module, OTAC-01.
4. Wrong value entered in parameter 5001 PULSE NR. A wrong value will only be detected if the error is such that the calculated slip is greater than 4 times the rated slip of the motor.
5. Encoder is not being used, but parameter 5002 ENCODER ENABLE = 1 ( ENABLE).