What causes an HMI COM FAULT on an ATV61 or ATV71 drive, and how can it be resolved?

An HMI COM FAULT occurs when the Human Machine Interface (HMI) loses communication with the drive.

In ATV61 and ATV71 drives, the HMI establishes a Modbus RTU connection during power-up, acting as the Modbus server. This communication is independent and isolated from the main Modbus/CANopen network.

⚠️ This fault only occurs when the drive is configured to receive start/stop commands and/or speed reference from the keypad (HMI).

When an HMI COM FAULT appears, check the following:

• Loose or disconnected cable

  • The cable between the drive and HMI may have been accidentally unplugged.

• Poor connection at the enclosure door

  • Opening the panel door may loosen the connection at the HMI mounting point.

• Control power issue (+10 V)

  • Verify the +10V to COM on the control terminals.
  • This is especially important if the HMI is mounted remotely (over 100 ft / 30 m), as voltage drop or interference may affect communication.

• Faulty HMI module

  • The HMI itself may be defective.
  • Replacement part: VW3A1101

• Damaged remote cable

  • If using a remote-mounted keypad, inspect the connecting cable.
  • Cable models:
    • VW3A1104R10 (1 m)
    • VW3A1104R30 (3 m)
    • VW3A1104R50 (5 m)
    • VW3A1104R100 (10 m)

An HMI COM FAULT is typically caused by a loss of communication between the keypad and the drive, often due to physical connection issues, power problems, or component failure. Checking cables, connections, and voltage supply usually resolves the issue quickly.