Rockwell Automation 20G PowerFlex 750-Series AC Drives - Manual (Page 273)

Rockwell Automation Publication 750-RM002B-EN-P - September 2013 273
Motor Control Chapter 4
Empirically setting values P314 [SLAT Err Stpt] and P315 [SLAT Dwell Time]
other than default may help create even smoother transitions.
Paper Winder Application Example
The drive is set for SLAT Minimum mode, so that the drive normally runs in
Torque mode and follows P675 [Trq Ref A Sel]. [Trq Ref A Sel] comes from an
external controller and is approximately 60% of motor torque during the
snapshot (shown below). The speed reference, also from an external controller, is
set just above the speed feedback to saturate the speed regulator while in Torque
mode. The following snapshot captures what occurs in the drive during a break in
the web.
Figure 34 - SLAT Min to Forced Speed Mode
+
–
P314 [SLAT Err Stpt]
P315 [SLAT Dwell Time]
Low Pass
Filter
Speed Error < 0
Off On
Speed Error > SLAT Setpoint
for SLAT Time
FSM State Controller
Application Dependant
Speed Reference Bias
Motor Speed Feedback
External Torque
Reference (ETR)
Speed Error
Speed Regulator
Output (SRO)
Forced Speed
Mode (FSM)
FSM - On
Off
PI
Regulator Min
Select
Internal Torque
Reference (ITR)
Small amount of overshoot
during web break.
Motor Speed Feedback (RPM)
Speed Regulator Out (%)
Speed Regulator Saturated
Motor Torque Reference (%)
Speed Error (RPM)
Speed Regulator is preloaded with
Motor Torque Reference.
Speed Error becomes negative.
Web break occurs.
Torque Mode Speed Mode