Installation manual

Danaher Motion Kollmorgen 08/04 Appendix B
SERVOSTAR S Installation M-SS-001-01 Rev. T 97
Commutation Tracks
The hall channels can be synthesized in the encoder or can be
discrete devices integrated in the motor windings. Commutation
tracks (hall channels) provide three digital channels that represent
alignment to the A-phase, B-phase, and C-phase back EMF of the
motor. An encoder with Hall channels must have the correct output
for the given pole count of the motor as the Hall signals are
referencing the motor's BEMF waveform.
Some systems use only hall channels for motor feedback
data. The channels provide enough information to commutate
a motor in an ON and OFF (trapezoidal) format but do not
provide enough information to properly commutate a motor
using sinusoidal control. Further, the coarse data is
insufficient to control velocity below a few hundred RPM. The
SERVOSTAR product is a high-performance controller and
does not support hall-only operation
.
Since encoders are incremental devices, a loss or gain of a pulse
creates system errors. Electrical noise is the single biggest factor in
miss-counts. Transmitting the signals differentially provides the
largest margin of noise rejection and the best signal fidelity. The
SERVO
STAR is designed to receive only differential signals. Some
less expensive encoders provide TTL or Open Collector signals.
These are not compatible with the SERVO
STAR.