Danfoss VLT FC 102 Programming Manual page 189

Parameter Descriptions
20-91 PID Anti Windup
Option: Function:
NOTICE
Option [1] On is activated
automatically, if 1 of the
following options is selected in
parameters in parameter group
21-** Ext. Closed Loop: [0]
Normal, [X] Enabled Ext CLX
PID.
[0] Off The integrator continues to change
value also after output has reached
1 of the extremes. This can
afterwards cause a delay of change
of the output of the controller.
[1] On The integrator is locked if the
*
output of the built-in PID controller
has reached 1 of the extremes
(minimum or maximum value) and
therefore is not able to add further
changes to the value of the process
parameter controlled. This allows
the controller to respond more
quickly when it can control the
system again.
20-93 PID Proportional Gain
Range: Function:
NOTICE
0.50 [0 - 10 ]
*
Always set the desired value
for parameter 20-14 Maximum
Reference/Feedb. before setting
the values for the PID
controller in parameter group
20-9* PID Controller.
The proportional gain indicates the
number of times the error between
the setpoint and the feedback
signal is to be applied.
If (Error x Gain) jumps with a value equal to what is set in
parameter 20-14 Maximum Reference/Feedb., the PID
controller tries to change the output speed equal to what
is set in parameter 4-13 Motor Speed High Limit [RPM]/
parameter 4-14 Motor Speed High Limit [Hz]. However, the
output speed is limited by this setting.
Calculate the proportional band (error causing output to
change from 0–100%) can be calculated with the formula:
1
× Max Reference
Proportional Gain
M0010001
Programming Guide
20-94 PID Integral Time
Range:
20 s
*
20-95 PID Differentiation Time
Range:
0 s
*
Danfoss A/S © 10/2019 All rights reserved.
Function:
[0.01 - 10000 The integrator accumulates a contri-
s] bution to the output from the PID
controller as long as there is a
deviation between the reference/
setpoint and feedback signals. The
contribution is proportional to the
size of the deviation. This ensures
that the deviation (error)
approaches zero.
Quick response on any deviation is
obtained when the integral time is
set to a low value. Setting it too
low, however, may cause the
control to become unstable.
The value set is the time needed
for the integrator to add the same
contribution as the proportional for
a certain deviation.
If the value is set to 10000, the
controller acts as a pure propor-
tional controller with a P-band
based on the value set in
parameter 20-93 PID Proportional
Gain. When no deviation is present,
the output from the proportional
controller is 0.
Function:
[0 - 10 s] The differentiator monitors the rate
of change of the feedback. If the
feedback is changing quickly, it
adjusts the output of the PID
controller to reduce the rate of
change of the feedback. Quick PID
controller response is obtained
when this value is large. However, if
too large of a value is used, the
frequency converter's output
frequency may become unstable.
Differentiation time is useful in
situations where extremely fast
frequency converter response and
precise speed control are required.
It can be difficult to adjust this for
proper system control. Differen-
tiation time is not commonly used
in HVAC applications. Therefore, it is
best to leave this parameter at 0 or
OFF.
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