Rockwell Automation 284 ArmorStart User Manual - Manual (Page 467)

Appendix
I
PID Setup
PID Loop The Bulletin 284 ArmorStart® Distributed Motor with sensorless
vector control has a built-in PID (proportional, integral, differential)
control loop. The PID loop is used to maintain a process feedback
(such as pressure, flow, or tension) at a desired set point. The PID
loop works by subtracting the PID feedback from a reference and
generating an error value. The PID loop reacts to the error, based on
the PID Gains, and outputs a frequency to try to reduce the error value
to 0. To enable the PID loop, Parameter 232 (PID Ref Sel) must be set
to an option other than 0 PID Disabled.
Exclusive Control and Trim Control are two basic configurations
where the PID loop may be used.
Exclusive Control
In Exclusive Control, the Speed Reference becomes 0, and the PID
Output becomes the entire Freq Command. Exclusive Control is used
when Parameter 232 (PID Ref Sel) is set to option 1, 2, 3, or 4. This
configuration does not require a master reference, only a desired set
point, such as a flow rate for a pump.
Example
•
In a pumping application, the PID Reference equals the Desired
System Pressure set point.
• The Pressure Transducer signal provides PID Feedback to the
drive. Fluctuations in actual system pressure, due to changes in
flow, result in a PID Error value.
• The drive output frequency increases or decreases to vary motor
shaft speed to correct for the PID Error value.
• The Desired System Pressure set point is maintained as valves in
the system are opened and closed causing changes in flow.
• When the PID Control Loop is disabled, the Commanded Speed
is the Ramped Speed Reference.
–
+
PID Prop Gain
PID Loop
PID Integ Time
PID Diff Rate
PID Enabled
PID Fdbk
PID Ref
PID
Error
+
+
+
PID
Output
Accel/Decel
Ramp
Freq
Command
Pump
PID Feedback =
Pressure Transducer Signal
PID Reference =
Desired System Pressure