9-1
9. Using PID Control for Constant Flow / Pressure Applications
9.1 What is PID Control?
The PID function in the inverter can be used to maintain a constant process variable such as pressure, flow,
temperature by regulating the output frequency (motor speed). A feedback device (transducer) signal is used to
compare the actual process variable to a specified setpoint.
The difference between the set-point and feedback signal is called the error signal.
The PID control tries to minimize this error to maintain a constant process variable by regulating the output
frequency (motor speed).
×1
-1
10-09
10-24
10-03=xx0xb
10-03=xx1xb
(Bias)
+
+ PID output gain
PID Output
±200% Limit
+
10-03=0xxxb
10-03=1xxxb
10-25=0
10-25=1
+109%
+109%
-109%
+
+
PID=0N
Frequency
reference
PID=OFF
10-04
10-07
10-05
10-06
10-10
+
Target
value
Feedback (10-01)
Feedback
gain
10-03=x0xxb
10-03=x1xxb
(D)
+
+
+
-
PID input
(Deviation)
(P)
(I)
(D)
100%
-
100%
10-14
(I-Limit)
+
+
+
Integral reset
(Using Multi-function
digital input)
10-03=x0xxb
10-03=x1xxb
100%
-100%
(PID Limit)
10-23
Primary delay
PID=OFF
1. 10-03=0 (PID disabled)
2. Dring JOG mode
3. Multi-function digital input (03-00~03-05=29)
10-07
Keypad display
10-00=0
AI1
AI2
Communication
10-00=1
10-00=2
10-00=3
10-02
10-00=4
The amplitude of the error can be adjusted with the Proportional Gain parameter 10-05 and is directly related to
the output of the PID controller, so the larger gain the larger the output correction.
