Allen-Bradley 22C-B012N103, Руководство пользователя

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158 Rockwell Automation Publication 22C-UM001J-EN-E - January 2017
Appendix D Application Notes
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
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[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
Fre q
Command
Pump
PID Feedback =
Pressure Transducer Signal
PID Reference =
Desired System Pressure