Alarm Display: A.C90 A.C91
Alarm Name: Encoder Communications Error & Encoder Communications Position Data Error
Situation at Alarm Occurrence: Occurred when the control power supply was turned ON or during operation.
Cause: The encoder wiring and the contact are incorrect.
Corrective Actions: Correct the encoder wiring.
Cause: Noise interference occurred due to incorrect encoder cable specifications.
Corrective Actions: Use tinned annealed copper twisted-pair or twisted-pair shielded wire with a core of at least 0.12 mm2 (0.0002 in2)
Cause: Noise interference occurred because the wiring distance for the encoder cable is too long.
Corrective Actions: The wiring distance must be 20m (65.6 ft) max.
Cause: The noise interference occurred on the signal line because the encoder cable is bent and the sheath is damaged.
Corrective Actions: Correct the encoder cable layout.
Cause: The encoder cable is bundled with a high-current line or near a high-current line.
Corrective Actions: Correct the encoder cable layout so that no surge is applied.
Cause: The FG varies because of the influence from machines on the servomotor side, such as welder.
Corrective Actions: Make the grounding for the machine separately from PG side FG.