Control Word Timeout
Danfoss · VLT Micro Drive FC 51
What does 10 mean?
This fault indicates that the drive has not received a valid control word via serial communication (e.g., Modbus RTU) within the configured timeout period. This typically means a break in communication, preventing the drive from receiving commands and potentially stopping the motor.
Common Causes
- Break in the serial communication cable (e.g., Modbus RTU RS-485) between the master device (PLC) and the drive.
- Incorrect Modbus communication parameters (e.g., baud rate P5-01, parity P5-02, slave address P5-00) configured on either the master or the drive.
- Modbus master device (e.g., PLC) not sending valid control words within the configured timeout period (Parameter P5-05).
- Faulty RS-485 transceiver chip on the drive's control board or the master device.
- Interference or noise on the communication line affecting data integrity.
Repair Steps & Checklist
Click steps to track your progress.
- 1
Visually inspect the RS-485 communication cable (e.g., twisted pair, shielded) for physical damage or loose connections at terminals (e.g., DA+, DB-).
- 2
Verify the Modbus communication settings (P5-00 to P5-05) on the drive match those configured in the Modbus master device (e.g., PLC program).
- 3
Monitor the communication line using a Modbus sniffer tool or oscilloscope to observe data packets and ensure control words are being sent.
- 4
Check for correct termination resistors (e.g., 120 Ohm) on the RS-485 bus, especially at the ends of the segment.
- 5
Temporarily connect a known good Modbus master (e.g., PC with Modbus poll software) to the drive to isolate the fault source.