Individual Functions
6
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65
Using PI Control
PI control is a method of making the feedback value (detection value) match the set target value. By combin-
ing proportional control (P) and integral control (I), you can even control targets (machinery) with play time.
The characteristics of the PI control operations are given below.
PI Control Operation
To understand the differences between the PI control operations P and I, the variation in the amount of opera-
tion (output frequency) is as shown in the following diagram when the deviation (i.e., the difference between
the target value and feedback value) is fixed.
Fig 6.42 PI Control Operation
PI Control Applications
The following table shows examples of PI control applications using the Inverter.
P control
Outputs the amount of operation proportional to the deviation. You cannot, however, set the
deviation to zero using P control alone.
I control
Outputs the amount of operation that integrates the deviation. Used for matching feedback
value to the target value.
Applica-
tion
Control Details
Example of
Sensor Used
Speed Con-
trol
• Feeds back machinery speed information and matches speed to the target value.
• Inputs speed information from other machinery as the target value and performs
synchronous control using the actual speed feedback.
Tachometer genera-
tor
Pressure
Control
Feeds back pressure information and performs parameter pressure control.
Pressure sensor
Flow Rate
Control
Feeds back flow rate information and controls the flow rate highly accurately.
Flow rate sensor
Tempera-
ture Con-
trol
Feeds back temperature information and performs temperature adjustment control by
rotating the fan.
• Thermocouple
• Thermistor
Deviation
Amount of operation
Time
P I c on trol
I control
P control
Time
