Using Pi Control - Omron VARISPEED E7 User Manual

Using PI Control

PI control is a method of making the feedback value (detection value) match the set target value.
The characteristics of the PI control operations are given below.
The output of a P-element is proportional to the input (deviation). With using a P-element alone it is
P element
not possible to eliminate the deviation completely.
The output of an I-element is the time-integral of the input (deviation). With using a P-element and an
I element
I-element together the deviation can be eliminated completely.
PID Control Operation
To understand the differences between the PI control operations P and I the output share of each operation is
shown in the following diagram when the deviation (i.e., the difference between the target value and feedback
value) is jumps to a certain value (step response).
Deviation
Output of P- and
I-element
PI Control Applications
The following table shows examples of PI control applications using the Inverter.
Application
Pressure Con-
Pressure information is fed back and constant pressure control is performed.
trol
Flow Rate Flow rate information is fed back and the flow rate is controlled with high accu-
Control racy.
Temperature Temperature information is fed back and a temperature adjustment control
Control using a fan can be performed.
Fig 6.56 PI Control Operation
Control Details
Individual Functions
Time
PI control
I control
P control
Time
Example of Sensor
Used
Pressure sensor
Flow rate sensor
• Thermocouple
• Thermistor
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