Commutation
As with commutating brushed dc motors, all brushless ac
permanent magnet motors require commutation information
to enable the drive to synchronise with the rotor of the motor.
Ideally, all feedback devices are aligned with the motor stator
during assembly. For those feedback devices that are not
aligned, the Unidrive has an Encoder Phasing Test (#3.25)
that automatically creates a Phase Position (Phase Offset)
value (#3.28).
Commutation Phase Offset
Most drives, including the Unidrive, provide for a “Phase
Offset” adjustment and a means of setting this to match a
motor with a different commutation setting.
All UM motor feedback devices are set to match the Unidrive
definition of zero offset*1, and similarly DM motor resolvers
are set to match the DigitAx drive, so that the drives may
operate with zero phase offset adjustment, thus allowing
interchange of motors between drives without further
adjustment.
Note that not all drives have the same zero offset definition.
All SL motors have built-in motor map definitions including
commutation information and are fully “plug & play” with
the M’Ax and MultiAx drives.
*1 Earlier motors with incremental encoders require a specific
non-zero phase offset value to be set in Unidrive