Moeller DF5 series - PID Controller; The PID Closed-Loop Control

Setting Parameters
09/01 AWB8230-1412GB
84
PID controller
The DF5 series frequency inverter is a PID controller. This can be
used, for example, for flow and throughput controllers with fans
and pumps. PID control has the following features:
• The setpoint value can be issued via the frequency inverter
keypad or via an external digital signal (fixed frequencies).
Sixteen different setpoint values are possible. In addition, the
setpoint can be defined with an analog input signal (0 to 10 V
or 4 to 20 mA).
• With the DF5, you can implement the actual value signal feed-
back through an analog input voltage (of up to 10 V) or an
analog input current (up to 20 mA).
• The permissible range for the actual value signal feedback can
be specifically matched (e.g. 0 to 5 V, 4 to 20 mA, or other
ranges).
• With the aid of a scale adjustment, you can match the setpoint
signal and/or the actual value signal to the actual physical
quantities (such as air or water flow, temperature, etc.) and
represent them on the display.
The PID closed-loop control
“P” stands for Proportional, “I” stands for Integral and “D”
stands for Differential. In control engineering, the combination of
these three terms is termed PID closed-loop control, PID regulation
or PID control. PID closed-loop control is used in numerous types
of application, e.g. for controlling air and water flow or for cont-
rolling pressure and temperature. The output frequency of the
inverter is controlled by a PID control algorithm to ensure that the
deviation between the setpoint and actual value is as small as
possible. The following figure shows a block diagram representa-
tion of a PID closed loop control:
Figure 81: PID closed-loop control block diagram
G1:frequency inverter DF5
w: Setpoint value
x: Actual value
P1: Controlled variable
B1: Measured value converter
a System deviation
b Converter
c Fans, pumps or similar devices
d Frequency setpoint value
B1
P1
x
c
b
d
a
M
3
~
I
P
D
+
w
G1
+
–
+
+
h
PID closed loop control is only possible after the type of
setpoint value and actual value used have been defined.