The ATV320 loses its link to the PLC or HMI over Modbus/Ethernet, showing a communication fault while the motor may still run on a local command.
These are the failure paths we see most often on the Schneider Electric ATV320 for a communication error condition. Likelihood reflects field frequency; First Check is what you can do remotely before sharing logs.
| Cause | Likelihood | First Check |
|---|---|---|
| Wrong Modbus address, baud or parity vs the master | High | Compare the drive's comm parameters to the PLC master settings |
| Termination or bias missing on a Modbus RS485 bus | Medium | Check the bus ends for 120 ohm termination and the bias resistors |
| Ethernet IP conflict or wrong subnet | Medium | Confirm the drive IP is unique and on the same subnet as the controller |
| Cable or shield fault on the comms line | Low–Medium | Inspect the comms cable for breaks and proper shielding/ground |
Work through these in order. Each step is something you can perform and report back on without opening the enclosure or swapping parts.
Read the drive's Modbus address, baud and parity and compare to the PLC master. A one-digit address or a parity mismatch silences the drive on the bus.
For Ethernet, confirm the link LED and a successful ping; for Modbus, check the bus termination and bias at both ends. A missing terminator causes intermittent errors.
Open the communication menu and confirm the protocol, address and the control/reference source match how the PLC talks to it. A mismatch means the PLC commands are ignored.
Note the exact communication fault code and when it appears — at power-up or under traffic. Constant loss points to wiring; loss under load points to termination.
After aligning address/baud/IP, confirm the PLC reads drive data and can start/stop it. Stable exchange for a few minutes means the link is fixed.
An ATV320 communication error is an addressing or wiring fault, not a dead drive. The bus termination, the address/baud match and a ping localize it immediately. Cross-reference the broader collections: Loss of communication · Industrial networking.
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Rarely. We align the address, baud and termination first; a card is only suspect if the link stays dead after that, and we confirm it.
Often yes, on a local command, while the link is down. We restore the link so the PLC regains control; the motor itself is usually fine.
On RS485, yes at the bus ends. Without it, reflections cause intermittent errors that look like a failing drive.
Share the comm parameters and the fault code. We align addressing and termination remotely so you avoid swapping a healthy comms card.
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When the fault is current, not the link.
A PLC-side link loss with a similar remote path.
Full pumps, motors & drives troubleshooting collection.