Cause : Modbus Communication Error comes when the communications cable wiring is incorrect or there is a short circuit in the communications cable or the communications cable is not connected.

1. Repair short circuits and connect cables.
2. Replace the defective communications cable.
3. Electrical interference caused a communication data error. 
4. Examine the control circuit lines, main circuit lines, and ground wiring, and decrease the effects of electrical interference. 
5. Make sure that a magnetic contactor is not the source of the electrical interference, then use a Surge Protective Device if necessary. 
6. Use only the recommended cables or other shielded line. Ground the shield on the controller side or the drive input power side.
7. Separate the communication wiring from drive power lines, and install a noise filter to the input side of the power supply for communication.
8. Decrease the effects of electrical interference from the controller.