Fieldbus/Serial Communication Lost

What does Com Error mean?

This fault indicates a loss of communication between the VSD and its control system via a serial or fieldbus network. This can be caused by cable issues, incorrect network settings, or a problem with the master controller. Loss of communication means the drive cannot receive commands or report its status, leading to uncontrolled operation or shutdown. It can halt processes relying on the drive's control.

• Physical damage to the fieldbus or serial communication cable (e.g., cut, loose connection, broken shield).
• Incorrect communication parameters (e.g., baud rate, parity, device address P5-02) mismatch between VSD and controller.
• Missing, incorrect, or double termination resistors on the fieldbus network (e.g., 120 Ohm for RS-485).
• Electromagnetic interference (EMI) on the communication lines due to unshielded cables or improper grounding.
• Internal failure of the VSD's communication interface module or an external option board.

Click steps to track your progress.

1. 1

   Visually inspect the communication cable for damage and confirm secure connections at VSD (e.g., RJ45) and control system. Measure cable continuity.

2. 2

   Verify VSD communication parameters (e.g., P5-01 protocol, P5-02 address, P5-03 baud rate) match the PLC or HMI configuration.

3. 3

   Check termination resistors at both ends of the fieldbus segment. Measure resistance across the bus lines at the last device.

4. 4

   Ensure proper grounding of communication cable shields at a single point (e.g., VSD control ground terminal) to minimize noise.

5. 5

   Test with a known good external communication converter or replace the VSD's communication option card (if applicable) to isolate the fault.