PID for process control
Feedback
The feedback signal must be connected to a terminal
on the adjustable frequency drive. Use the list below
to decide which terminal is to be used and which pa-
rameters are to be programmed.
Feedback type Terminal Parameters
Pulse 33 307
Voltage 53 308, 309, 310
Current 60 314, 315, 316
Furthermore, the minimum and maximum feedback
(parameters 414 and 415) must be set to a value in the
process unit that corresponds to the minimum and
maximum value on the terminal.
Select process unit in parameter 416.
Reference
A minimum and a maximum reference can be set (204
and 205), which limit the sum of all references. The
reference range cannot exceed the feedback range.
If one or several setpoint references are required, the
simplest way is to set such reference directly in pa-
rameters 215 to 218. Select between the preset refer-
ences by connecting terminals 16, 17, 29, 32 and/or
33 to terminal 12. Which terminals that are used de-
pends on the choice made in the parameters of the
various terminals (parameters 300, 301, 305, 306 and/
or 307). Use the table below when selecting preset
references.
Preset ref. msb Preset ref. lsb
Preset ref. 1
(par. 215)
00
Preset ref. 2
(par. 216)
01
Preset ref. 3
(par. 217)
10
Preset ref. 4
(par. 218)
11
If an external reference is required, this can either be
an analog or a pulse reference. If current is used as a
feedback signal, only voltage can be used as an ana-
log reference. Use the following list to decide which
terminal to use and which parameters to program.
Reference type Terminal Parameters
Pulse 17 or 29 301 or 305
Voltage 53 or 54 308, 309, 310 or
311, 312, 313
Current 60 314, 315, 316
Relative references can be programmed. A relative
reference is a percentage value (Y) of the sum of the
external references (X). This percentage value is add-
ed to the sum of the external references, which pro-
duces the active reference (X + XY). See section
Handling of multi references.
If relative references are to be used, parameter 214 is
to be set to Relative [1]. This makes the preset refer-
ences relative. Furthermore, Relative reference [4] can
be programmed on terminal 54 and/or 60. If an exter-
nal relative reference is selected, the signal on the
input will be a percentage value of the full range of the
terminal. The relative references are added with signs.
NOTE
Terminals that are not in use should pref-
erably be set to No function [0].
Inverse control
If the drive has to react with increasing speed on and
increasing feedback, Inverse must be selected in pa-
rameter 437. Normal control means that the motor
speed decreases when the feedback signal increases.
Anti Windup
The process controller comes with the anti windup
function in active position. This function ensures that
when either a frequency limit or a torque limit is
reached, the integrator will be set to a gain that corre-
sponds to the actual frequency. This avoids integrating
on an error that cannot in any case be compensated
for by means of a speed change. This function can be
disabled in parameter 438.
Start-up conditions
In some applications, optimum setting of the process
controller will mean that it takes an excessive time for
the desired process value to be reached. In such ap-
plications it might be an advantage to fix a motor
frequency to which the adjustable frequency drive is to
bring the motor before the process controller is acti-
vated. This is done by programming a Process PID
start frequency in parameter 439.
VLT
®
5000 Series
200 MG.51.C5.22 - VLT
p
is a registered Danfoss trademark.
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