Installation manual

Danaher Motion Kollmorgen Appendix C
SERVOSTAR
®
S and SERVOSTAR
®
CD Series 116
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 MENCTYPE 1,
MENCTYPE 2, MENCTYPE 3, and 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.
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.
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
MECNOFF variable. Caution must be exercised as motors may generate lethal
voltages when rotating.