P 7-30
normal/inverse
PID
P 7-38
*(-1)
Feed forward
Ref.
Handling
Feedback
Handling
% [unit]
% [unit]
%
[unit]
%
[speed]
Scale to
speed
P 4-10
Motor speed
direction
To motor
control
Process PID
130BA178.10
_
+
0%
-100%
100%
0%
-100%
100%
Illustration 16.2 Process PID Control Diagram
16.2.1 Process PID Control Parameters
The following parameters are relevant for the process control
Parameter
Description of function
Parameter 7-20 Process CL
Feedback 1 Resource
Selects from which input the process PID gets its feedback.
Parameter 7-22 Process CL
Feedback 2 Resource
Optional: Determines if and from where the process PID gets an additional feedback signal. If an additional
feedback source is selected, the 2 feedback signals are added before being used in the process PID
control.
Parameter 7-30 Process PID
Normal/ Inverse Control
Under
[0] normal operation
, the process control responds with an increase of the motor speed if the
feedback lower than the reference. In the same situation, but under
[1] inverse operation
, the process
control responds with a decreasing motor speed.
Parameter 7-31 Process PID
Anti Windup
The anti-windup function ensures that when either a frequency limit or a torque limit is reached, the
integrator is set to a gain that corresponds to the actual frequency. This function avoids integrating on an
error that cannot be compensated with a speed change. Disable this function by selecting
[0] Off
.
Parameter 7-32 Process PID
Start Speed
In some applications, reaching the required speed/setpoint can take a long time. In such cases, it is
beneficial to set a fixed motor speed from the frequency converter before the process control is activated.
Set the fixed motor speed by setting a process PID start value (speed) in
parameter 7-32 Process PID Start
Speed
.
Parameter 7-33 Process PID
Proportional Gain
The higher the value, the quicker the control. However, too large a value can lead to oscillations.
Parameter 7-34 Process PID
Integral Time
Eliminates steady state speed error. Lower value means quick reaction. However, too small a value can lead
to oscillations.
Parameter 7-35 Process PID
Differentiation Time
Provides a gain proportional to the rate of feedback change. A setting of 0 disables the differentiator.
Parameter 7-36 Process PID
Diff. Gain Limit
If there are quick changes in reference or feedback in a given application, the differentiator gain can be
limited to allow setting of a reasonable differentiation time for slow error changes.
Parameter 7-38 Process PID
Feed Forward Factor
In applications where there is a good and approximately linear correlation between the process reference
and the motor speed necessary for obtaining that reference, the feed forward factor can be used to
achieve better dynamic performance of the process PID control.
PID Controls
Design Guide
MG37N102
Danfoss A/S © 6/2016 All rights reserved.
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