Danfoss VLT FC 100 Series Programming Manual page 149

Parameter Description
20-91 PID Anti Windup
Option: Function:
[0] Off Off [0] The integrator will continue to change value
3 3
also after output has reached one of the extremes.
This can afterwards cause a delay of change of the
output of the controller.
[1] On On [1] The integrator will be locked if the output of
*
the built-in PID controller has reached one of the
extremes (min or max value) and therefore not able to
add further change to the value of the process
parameter controlled. This allows the controller to
respond more quickly when it again can control the
system.
20-93 PID Proportional Gain
Range:
0.50 [0.00 - 10.00 ] The proportional gain indicates the
*
If (Error x Gain) jumps with a value equal to what is set in
20-14 Maximum Reference/Feedb., the PID controller will try
to change the output speed equal to what is set in
4-13 Motor Speed High Limit [RPM]/4-14 Motor Speed High
Limit [Hz] but in practice of course limited by this setting.
The proportional band (error causing output to change
from 0‒100%) can be calculated by means of the formula:
(
1
Proportional Gain
NOTE!
Always set the desired for 20-14 Maximum Reference/Feedb.
before setting the values for the PID controller in
parameter group 20-9*.
20-94 PID Integral Time
Range:
20.00 [0.01 -
s 10000.00
*
s]
3-122
Function:
number of times the error between the
setpoint and the feedback signal is to be
applied.
)
× ( Max Reference )
Function:
Over time, the integrator accumulates a
contribution to the output from the PID
controller as long as there is a deviation
between the reference/setpoint and
feedback signals. The contribution is propor-
tional 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.
MG11CD22 - VLT
®
VLT HVAC Drive Programming Guide
20-94 PID Integral Time
Range:
20-95 PID Differentiation Time
Range:
0.00
s
*
20-96 PID Diff. Gain Limit
Range:
5.0 [1.0 -
*
50.0 ]
® is a registered Danfoss trademark
Function:
If the value is set to 10,000, the controller
will act as a pure proportional controller
with a P-band based on the value set in
20-93 PID Proportional Gain. When no
deviation is present, the output from the
proportional controller will be 0.
Function:
[0.00 - The differentiator monitors the rate of change
10.00 s] of the feedback. If the feedback is changing
quickly, it will adjust 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 a
value that is too large is used, the adjustable
frequency drive's output frequency may become
unstable.
Differentiation time is useful in situations where
extremely fast adjustable frequency drive
response and precise speed control are
required. It can be difficult to adjust this for
proper system control. Differentiation time is
not commonly used in VLT
applications. Therefore, it is generally best to
leave this parameter at 0 or OFF.
Function:
The differential function of a PID Controller
responds to the rate of change of the feedback.
As a result, an abrupt change in the feedback
can cause the differential function to make a
very large change in the PID Controller's output.
This parameter limits the maximum effect that
the PID Controller's differential function can
produce. A smaller value reduces the maximum
effect of the PID Controller's differential function.
This parameter is only active when 20-95 PID
Differentiation Time is not set to OFF (0 s).
®
HVAC Drive