Rockwell Automation 9VT201-007HTNNN, User Manual, Page: 202 / 224

C-6 Application Notes
Publication 9VT-UM001D-EN-P
Figure C.3 Power Loss Mode = Decel
The internal PI function of theVTAC 9 provides closed loop process
control with proportional and integral control action. The function is
designed for use in applications that require simple control of a process
without external control devices. The PI function allows the
microprocessor of the drive to follow a single process control loop.
The PI function reads a process variable input to the drive and compares
it to a desired setpoint stored in the drive. The algorithm will then adjust
the output of the PI regulator, changing drive output frequency to try and
make the process variable equal the setpoint.
It can operate as trim mode by summing the PI loop output with a master
speed reference.
Or, it can operate as control mode by supplying the entire speed
reference. This method is identified as “exclusive mode”
N ominal
82%
Bus Voltage
M otor S peed
Output Enable
Power Loss
Process PI
+
S pd Cmd
Process PI
Controller
Linear R amp
& S -Curve
+
+
+
PI Enabled S peed Control
S pd R ef
PI R ef
PI Fbk
S lip A dder
Open
Loop
S lip
Comp
Process
PI
S pd Cmd
Process PI
Controller
Linear R amp
& S -Curve
+
+
PI Enabled
S peed Control
S pd R ef
PI R ef
PI Fbk
S lip A dder
Open
Loop
S lip
Comp
Process
PI