Pid For Process Control - Danfoss AKD 5001 Manual

PID for process control

Feedback
The feedback signal must be connected to a terminal
on the frequency converter. Use the list below to
decide which terminal is to be used and which
parameters are to be programmed.
Feedback type Terminal
Pulse 33
Voltage 53
Current 60
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 parameters 215 to 218. Select between the
preset references by connecting terminals 16, 17,
29, 32 and/or 33 to terminal 12. Which terminals
that are used depends 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. 1 0
(par. 215)
Preset ref. 2 0
(par. 216)
Preset ref. 3 1
(par. 217)
Preset ref. 4 1
(par. 218)
If an external reference is required, this can either
be an analogue or a pulse reference. If current
is used as a feedback signal, only voltage can
be used as an analogue reference. Use the
following list to decide which terminal to use and
which parameters to program.
Reference type Terminal
Pulse 17 or 29
Voltage 53 or 54
Current 60
54
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 added to the sum of the external references,
which produces the active reference (X + XY). See
section Handling of multi references.
If relative references are to be used, parameter 214 is to
Parameters
be set to Relative [1]. This makes the preset references
307
relative. Furthermore, Relative reference [4] can be
308, 309, 310
programmed on terminal 54 and/or 60. If an external
314, 315, 316
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.
Inverse control
If the drive has to react with increasing speed on
and increasing feedback, Inverse must be selected in
parameter 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
corresponds to the actual frequency. This avoids
integrating on an error that cannot in any case be
compensated for by means of a speed change.
Preset ref. lsb
0
Start-up conditions
In some applications, optimum setting of the process
1
controller will mean that it takes an excessive time
for the desired process value to be reached. In
0
such applications it might be an advantage to fix a
motor frequency to which the frequency converter is
1
to bring the motor before the process controller is
activated. This is done by programming a Process
PID start frequency in parameter 439.
Lowpass filter
If there are oscillations of the current/voltage feedback
signal, these can be dampened by means of a lowpass
filter. Set a suitable lowpass filter time constant. This
time constant represents the limitfrequency of the
ripples occurring on the feedback signal. If the lowpass
Parameters
filter has been set to 0.1s, the limit frequency will be 10
301 or 305
RAD/sec., corresponding to (10/2 x π) = 1.6 Hz. This
308, 309, 310 or
will mean that all currents/voltages that vary by more
311, 312, 313
than 1.6 oscillations per second will be removed by
314, 315, 316
the filter. In other words, control will only be carried
out on a feedback signal that varies by a frequency of
AKD 5000
NB!:
Terminals that are not in use should preferably
be set to No function [0].
MG.50.R3.02 -