Applicable Systems
PLC
Symptoms
The PLC reports a feedback signal loss. The motor feedback device signal was lost, disabling closed-loop control.
Possible Causes
- Encoder or resolver cable disconnected or damaged
- Feedback device internal electronics failure
- Feedback signal processing circuit failure in the drive
Troubleshooting Steps
- Step 1: Check the feedback device cable connection at both ends
Cable is properly connected - Step 2: Test the feedback device output signal with an oscilloscope
Feedback signal is present and correct - Step 3: If the feedback device is faulty, replace the motor or encoder
New feedback device provides stable signal
How to Reset
To reset: Restore the feedback signal, then reset and restart.
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Source: B&R Automation System Manual, B&R Industrial Automation
Category: PLC & VFD
Published: 2026-10-01
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