Rockwell Automation 25B PowerFlex 520-Series Adjustable Frequency AC Drive User Manual - Manual (Page 206)

206 Rockwell Automation Publication 520-UM001G-EN-E - September 2014
Appendix E Encoder/Pulse Train Usage and Position StepLogic Application
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 1cm 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 one 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 Step Logic Commands settings and instead the drive will move
directly to whatever step is currently commanded by
A410 ... A425 [Preset
Freq x] and L200 ... L214 [Step Units x]. This is useful when an application