Rockwell Automation Publication MOTION-UM003K-EN-P - January 2019 233
Commission an Axis Chapter 11
Verification of Known Commutation Offset
Another use of the Commutation Test is to verify that the motor is wired
correctly and has the expected Commutation Offset. A machine engineer can
decide not to correct for a wiring error in software but rather flag a wiring error
so that it can be physically corrected. Incorrect wiring of the motor power
phases, encoder signal wiring, or commutation signal wiring can show up as an
unexpected Commutation Offset.
For example, suppose that a motor was wired in a ‘WUV’ sequence instead of
the normal ‘UVW’ sequence. The motor would still rotate in the correct
direction, but the Commutation Test indicate that the Commutation Offset
was off by a factor of 120 electrical degrees.
After running the Motor and Feedback Hookup Tests, you can run the
Commutation Test to determine the specific Commutation Offset and
Commutation Polarity. The drive executes the Commutation Test, which
includes motor rotation in the positive direction by at least one revolution. The
results of the Commutation Test are reported back to compare against the
known Commutation Offset and Commutation Polarity to determine if a
wiring issue exists.
Non-standard or Incorrect Wiring
The Commutation Test can also be applied to a PM motor that is wired in a
non-standard manner or incorrectly. If there is incorrect wiring, it is sometimes
desirable to mitigate the problem via software. You can use software mitigation
on larger machines where changes to the wiring would be difficult due to the
size and location of the wiring.
After running the Motor and Feedback Hookup Tests, you can run the
Commutation Test to determine the specific Commutation Offset and
Commutation Polarity. The drive executes the Commutation Test, which
includes motor rotation in the positive direction by at least one revolution. The
results of the Commutation Test are reported back for review. If the results are
satisfactory, you can accept the results as part of the stored axis configuration of
the controller to establish the correct wiring polarity.
To Next Page
Loading...
Need help?
General
