Danfoss VLT AQUA Drive FC 200 Programming Manual page 135

Parameter Description
20-93 PID Proportional Gain
Range:
2.00 [0.00 - 10.00 ] The proportional gain indicates the
*
3 3
If (Error x Gain) jumps with a value equal to what is set in
3-03 Maximum Reference 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 value for 3-03 Maximum Reference
before setting the values for the PID controller in
parameter group 20-9* PID Controller.
20-94 PID Integral Time
Range:
8.00 [0.01 -
s 10000.00
*
s]
20-95 PID Differentiation Time
Range:
0.00 [0.00 -
s 10.00 s]
*
134
Function:
number of times the error between the
set point 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.
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:
The differentiator monitors the rate of change
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
too large of a value is used, the frequency
MG20O602 - VLT
®
VLT AQUA Drive Programming Guide
20-95 PID Differentiation Time
Range:
20-96 PID Diff. Gain Limit
Range:
5.0 [1.0 -
*
50.0 ]
®
is a registered Danfoss trademark
Function:
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. Differentiation time is not commonly
used in water/ wastewater 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).