21-18 Ext. 1 Feedback [Unit]
Range: Function:
0.000 Ex-
tPID1Unit*
[-999999.999 - 999999.999 Ex-
tPID1Unit]
Readout of the feedback value for the Closed Loop 1 Controller.
21-19 Ext. 1 Output [%]
Range: Function:
0 %* [0 - 100 %] Readout of the output value for the Closed Loop 1 Controller.
3.19.4 21-2* Closed Loop 1 PID
Configure the Closed Loop 1 PID controller.
21-20 Ext. 1 Normal/Inverse Control
Option: Function:
[0] * Normal Select
Normal
[0] if the output should be reduced when feedback is higher than the reference.
[1] Inverse Select
Inverse
[1] if the output should be increased when feedback is higher than the reference.
21-21 Ext. 1 Proportional Gain
Range: Function:
0.01 N/A* [0.00 - 10.00 N/A]
If (Error x Gain) jumps with a value equal to what is set in par. 20-14
Maximum Reference/Feedb.
, the PID controller will try to change the output speed
equal to what is set in par. 4-13/4-14, Motor Speed High Limit, 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
)
×
(
Max
Reference
)
NB!
Always set the desired for par. 20-14
Maximum Reference/Feedb.
before setting the values for the PID controller in par. group 20-9*.
21-22 Ext. 1 Integral Time
Range: Function:
10000.00
s*
[0.01 - 10000.00 s] 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
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
part 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 par. 20-93
PID Proportional Gain
. When no deviation is present, the output
from the proportional controller will be 0.
21-23 Ext. 1 Differentation Time
Range: Function:
0.00 s* [0.00 - 10.00 s] The differentiator does not react to a constant error. It only provides a gain when the feedback
changes. The quicker the feedback changes, the stronger the gain from the differentiator.
3 Parameter Description VLT
®
HVAC Drive Programming Guide
194
MG.11.C9.02 - VLT
®
is a registered Danfoss trademark
3
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