Installation manual

Danaher Motion Kollmorgen 08/04 Appendix B
SERVOSTAR S Installation M-SS-001-01 Rev. T 103
B.1.3 COMMUTATION ACCURACY
The accuracy of the commutation alignment within the drive affects
the overall system efficiency. Misalignment also causes greater
torque ripple. As a general estimator, the following equation holds:
K
t effective
= K
t Rated
* Cosine (Alignment Error)
Inaccuracy of commutation alignment can occur from multiple
sources when using encoders. The accuracy of the hall channel
devices, if they are provided from an encoder using an optical disc,
are typically accurate to 5º or better electrically. When they are
integral to the motor, they may have an error of up to 15º. Using the
above equation, a 15º error would still provide more than 96% of
the motor's torque.
The accuracy of the 'wake and shake' algorithms used in B.1.2.2
MENCTYPE 1, B.1.2.3 MENCTYPE 2, B.1.2.4
MENCTYPE 3, and B.1.2.5 MENCTYPE 4 are subject
to many outside influences, such as friction and inertia. These
algorithms are not robust and are subject to varying amounts of
error.
Incorrect commutation alignment also causes differences in
efficiency according to direction. In an exaggerated example, a
misaligned commutation angle may allow a 1500 RPM motor to go
2000 RPM in one direction and only 1000 RPM in the other.
B.1.4 PHYSICAL ENCODER ALIGNMENT
The SERVOSTAR provides a number of features (variables) to
allow adjustment of the encoder signal alignment through the
software. These features can be very useful, but you must be
careful when using them. If the alignment of the encoder to the
motor is left to chance, swapping out the motor or encoder requires
that these variables be recalibrated for the new alignment. Is this
acceptable in the given application? You may not be certain that
the knowledge to do so will remain in the future. A better method is
to align the encoder on the motor. This makes swap-out a simpler
process.
B.1.2.1 MENCTYPE 0 (A/B/I and Halls) has hall channels
aligned to the motors back EMF. This is accomplished by rotating
the motor via an external source, monitoring the signals from the
hall effect channels while monitoring the voltage generated by the
motor and rotating the encoder housing until the waveforms
overlap. The encoder mounting screws are then secured. This
aligns the hall channels and the marker channel must then be
aligned using the B.1.5 MECNOFF variable.
Caution must
be exercised as motors may generate lethal voltages when
rotating.