Rockwell Automation 20P PowerFlex Digital DC Drive - Manual (Page 297)

Rockwell Automation Publication 20P-UM001I-EN-P - February 2013 297
Application Notes Appendix C
SLAT MAX Mode
In SLAT Max mode, the user would typically configure a speed reference that
forces the speed regulator into saturation (the speed reference is slightly below
the speed feedback). In this case the drive would follow the torque reference until
there was a breakage or slippage in the application.
In SLAT Max mode, the drive will switch from torque mode to speed mode when
either one of the two following conditions occur:
1. The output of the speed regulator becomes more than the torque
reference. This is speed mode.
2. The speed error becomes positive (the speed feedback becomes less than
the speed reference). This is forced speed mode.
Parameter 15 [SLAT Err Stpt] and parameter 16 [SLAT Dwell Time] allow you
to set some hysteresis for turning off the forced speed mode. They are set to “0” as
default so that there is no hysteresis. In SLAT Max mode, Par 15 [SLAT Err Stpt]
sets how much more the speed feedback should be than the speed reference
before turning off the forced speed mode. Par 16 [SLAT Dwell Time] sets how
long the speed error must exceed the SLAT error set point before turning off the
forced speed mode.
At the time the drive switches from torque mode to forced speed mode, the speed
regulator integral part is pre-loaded with the InternalTorque Reference (ITR) or
Par 14 [Selected TorqRef ] to create a smooth transition.
In order for the drive to switch from speed mode to torque mode, forced speed
mode (if active) must first be turned off. Forced speed mode will turn off when
the speed error is less than the SLAT error setpoint for the SLAT Dwell Time.
With default parameter settings, this will occur when the speed error becomes
negative.
When Forced Speed Mode is off, the drive will switch back to torque mode when
the speed regulator output becomes less than the torque reference.
Application
Dependant Speed
Reference Bias
Motor Speed
Feedback
+
-
Speed Error
PI
Regulator
Speed Regulator
Output (SRO)
Max
Select
External Torque
Reference (ETR)
Internal Torque
Reference (ITR)
Off
Forced Speed
Mode (FSM)
FSM = On
Low Pass
Filter
On Off
Speed Error > 0
Speed Error < -SLAT Setpoint
for SLAT Time
FSM State Controller
Par 15 [SLAT Err Stpt]
Par 16 [SLAT Dwell Time]