Motor Rotating

What does ALARM 126 mean?

A high back EMF voltage has been detected, indicating that the Permanent Magnet (PM) motor is rotating while the drive is attempting to control or start it. This can interfere with the drive's control algorithms and prevent a successful start.

• External mechanical force (e.g., windmilling fan, moving conveyor) causing the Permanent Magnet (PM) motor shaft to rotate.
• Drive attempting to start a PM motor that is already rotating, without a 'Flying Start' function (e.g., Parameter P1-80) properly enabled or configured.
• Brake not fully engaged or failing to hold the motor stationary before a start command is issued, allowing residual rotation.
• Faulty motor feedback device (encoder, resolver) wiring or incorrect calibration causing misdetection of motor speed during startup sequence.

Click steps to track your progress.

1. 1

   Verify motor shaft is mechanically stationary before issuing a run command using a visual inspection or a handheld tachometer.

2. 2

   Check Parameter P1-80 ('Flying Start') setting; ensure it is enabled (e.g., set to 'Auto' or 'Enable') to allow controlled startup into a rotating motor.

3. 3

   Measure the AC voltage across motor terminals U, V, W while the drive is stopped; investigate if significant voltage is present, indicating external rotation.

4. 4

   Inspect and test the operation of any external mechanical brake; confirm it fully engages and holds the motor stationary when the drive is not running.

5. 5

   Verify continuity and proper shielding of the motor feedback cable at the drive's respective input terminals (e.g., X33/X34 for encoder).