NSK EDD Megatorque Motor, User Manual, Page: 352 / 398

11. Alarm and Warning
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11.3.8. Alarm A9: Commutation Error

The Driver Unit checks if the Motor operates normally at the moment of the first servo activation after the
power is turned on.
This alarm occurs when the Motor moves exceeding ± 15° (angle degree) at this moment.
Table 11-15: Cause and Remedy for the Alarm A9
Cause Remedy
(1)
Unmatched combination of Motor
and Driver Unit.

Check for proper combination
(2)
The Motor moves when the servo is
turned on because of external force.

Remove the cause of external force.

Refer to “5. Tuning” if the Motor is affected by the gravity because its axis
is horizontal.
(3) Defective cable, Motor or Driver Unit.

Follow “Appendix 2: How to Check Motor Condition” for checking their
conditions. Replace the cable or the Motor if necessary.

If above procedures do not work, the Driver Unit nay be defective. Replace
it referring to “Appendix 5: Procedure for Replacing Driver Unit Model
EDD.”