20-93 PID Proportional Gain
Range:
Function:
0.50
*
[0 -
10 ]
NOTICE
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.
The proportional band (error causing output to change
from 0–100%) can be calculated with the formula:
1
Proportional Gain × Max Reference
20-94 PID Integral Time
Range:
Function:
20
s
*
[0.01 -
10000 s]
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 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 proportional controller with a P-band
based on the value set in
. When no deviation is present,
the output from the proportional controller is 0.
20-95 PID Differentiation Time
Range:
Function:
0 s
*
[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.
20-95 PID Differentiation Time
Range:
Function:
Differentiation time is useful is 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
HVAC applications. Therefore, it is best to leave
this parameter at 0 or OFF.
20-96 PID Diff. Gain Limit
Range:
Function:
5
*
[1 -
50 ]
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
parameter 20-95 PID Differentiation Time
is not set
to OFF (0 s).
Parameter Descriptions
VLT
®
HVAC Drive FC 102
150
Danfoss A/S © 03/2015 All rights reserved.
MG11CE02
3
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