Danfoss VLT Series Programming Manual page 143

Parameter Description
21-15 Ext. 1 Setpoint
Range:
0.000
ExtPID1Unit
*
3 3
21-17 Ext. 1 Reference [Unit]
Range:
0.000
ExtPID1Unit
*
21-18 Ext. 1 Feedback [Unit]
Range:
0.000
ExtPID1Unit
*
21-19 Ext. 1 Output [%]
Range:
0 % [0 - 100 %] Readout of the output value for the Closed
*
3.19.3 21-2* Closed Loop 1 PID
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:
0.01 [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
142
Function:
[-999999.999 - The setpoint reference is
999999.999 used in extended 1 closed
ExtPID1Unit] loop. Ext.1 Setpoint is added
to the value from the Ext.1
Reference source selected in
21-13 Ext. 1 Reference Source.
Function:
[-999999.999 - Readout of the
999999.999 reference value for the
ExtPID1Unit] Closed Loop 1
Controller.
Function:
[-999999.999 - Readout of the
999999.999 feedback value for the
ExtPID1Unit] Closed Loop 1
Controller.
Function:
Loop 1 Controller.
Function:
number of times the error between the
set point and the feedback signal is to be
applied.
)
× ( Max Reference )
MG.11.CC.02 - VLT
®
VLT HVAC Drive Programming Guide
NOTE
Always set the desired for 20-14 Maximum Reference/Feedb.
before setting the values for the PID controller in
parameter group 20-9*.
21-22 Ext. 1 Integral Time
Range:
10000.00
s
*
21-23 Ext. 1 Differentation Time
Range:
0.00 s
*
21-24 Ext. 1 Dif. Gain Limit
Range:
5.0 [1.0 - 50.0 ] Set a limit for the differentiator gain (DG).
*
®
is a registered Danfoss trademark
Function:
[0.01 - Over time, the integrator accumulates a
10000.00 contribution to the output from the PID
s] 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 20-93 PID Proportional Gain.
When no deviation is present, the output
from the proportional controller will be
0.
Function:
[0.00 - 10.00 The differentiator does not react to a
s] constant error. It only provides a gain
when the feedback changes. The quicker
the feedback changes, the stronger the
gain from the differentiator.
Function:
The DG will increase if there are fast
changes. Limit the DG to obtain a pure
differentiator gain at slow changes and a
constant differentiator gain where quick
changes occur.