User manual

158 Rockwell Automation Publication MOTION-UM003F-EN-P - March 2015
Chapter 7 Commission
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 may
not want to correct for a wiring error in software but rather flag a wiring error so
that it may be physically corrected. Incorrect wiring of the motor power phases,
encoder signal wiring, or commutation signal wiring may 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 rotating the motor 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. In the case of incorrect wiring, it is sometimes
desirable to mitigate the problem via software. This can be the case on larger
machines where changing 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 rotating the motor in the positive direction by at least one revolution.
The results of the Commutation Test are reported back for review, and, if found
satisfactory, you can accept the results as part of the controller’s stored axis
configuration that is sent to the drive during initialization to establish the correct
wiring polarity.