Rockwell Automation Allen-Bradley PowerFlex 520 Series, User Manual, Page: 221 / 272

Rockwell Automation Publication 520-UM001K-EN-E - August 2021 221
Appendix E Encoder/Pulse Train Usage and Position StepLogic Application
results, tune the application first. The autotune routine can be completed to
further improve the drive-motor performance.
A550 [Bus Reg Enable] default setting is 1 “Enabled”. If the deceleration time is
too short, the drive may overshoot the desired position. For best results, a
longer deceleration time may be necessary.
A550 [Bus Reg Enable] can be
disabled to provide precise stopping movements, but the deceleration time will
need to be manually tuned so that it is long enough to avoid F005
“OverVoltage” faults.
A437 [DB Resistor Sel] default setting is 0 “Disabled”. If improved deceleration
performance is required a Dynamic Brake resistor can be used. If used, this
parameter should be set to the appropriate setting for the resistor selected.
P035 [Motor NP Poles] must be set to match the number of motor poles on the
motor driven by the PowerFlex 520-series drive.
A536 [Encoder PPR] must be set to match the number of pulses per revolution
of the encoder used (i.e., 1024 PPR Encoder).
A559 [Counts Per Unit] sets the number of encoder counts that will be used to
define one position unit. This allows the encoder positions to be defined in
terms of units important to the application. For example, if 1 cm of travel on a
conveyor belt requires 0.75 turns of the motor, the motor encoder is 1024 PPR,
and the Motor Feedback type is set to Quadrature, then this parameter would
need to be set to (4 x 1024 x 0.75) = 3072 counts for 1 cm of travel. Then all other
positions could be setup in units of “cm”.
A564 [Encoder Pos Tol] indicates the desired position tolerance for the system.
This will determine how close the drive must be to the commanded position
before the drive will indicate “At Home” or “At Position” in units of raw
encoder pulses. This has no effect on the actual positioning control of the
motor.
Positioning Operation
Parameter A558 [Positioning Mode] must be set to properly match the desired
operation of the positioning function.
A558 [Positioning Mode] Options
0 “Time Steps” uses Step Logic times. This mode ignores the Step
Logic settings and moves through the steps (Step 0 to Step 7 and back
to Step 0) based on the times programmed into
L190 ... L197 [Stp Logic
Time x]. This can be used when the desired position is based only on
time. In addition, this mode only accepts absolute positions in a
positive direction from “home”. This option provides an easy way to
implement a simple positioning program or to test the basic
positioning setup. For additional flexibility one of the other settings
should be used.
1 “Preset Input” directly commands movement to any step based on
the status of the digital inputs programmed for “Preset Freq”. This
setting ignores the StepLogic Commands settings and instead the