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PID Controls
Function
Set terminal 53 low voltage:
Set terminal 53 high voltage:
Set terminal 54 low feedback value:
Set terminal 54 high feedback value:
Set feedback source:
6) Basic PID settings.
Process PID normal/inverse.
Process PID anti wind up.
Process PID start speed.
Save parameters to LCP.
Table 16.6 Example of Process PID Control Set-up
16.2.4 Process Controller Optimization
After the basic settings have been made, optimize the
following:
•
Proportional gain
•
Integration time
•
Differentiation time
In most processes, the basic settings can be done by
following these steps:
1.
Start the motor.
2.
Set parameter 7-33 Process PID Proportional Gain
to 0.3 and increase it until the feedback signal
begins to vary continuously. Then reduce the
value until the feedback signal has stabilized.
Now lower the proportional gain by 40–60%.
3.
Set parameter 7-34 Process PID Integral Time to 20
16
16
s and reduce the value until the feedback signal
begins to vary continuously. Increase the
integration time until the feedback signal
stabilizes, followed by an increase of 15–50%.
4.
Only use parameter 7-35 Process PID Differentiation
Time for very fast-acting systems only (differen-
tiation time). The typical value is 4 times the set
integration time. Only use the differentiator when
the setting of the proportional gain and the
integration time are fully optimized. Make sure
that the low-pass filter sufficiently dampens the
oscillations on the feedback signal.
150
®
VLT
Parallel Drive Modules
Parameter
Setting
Parameter 6-10 Terminal
0 V
53 Low Voltage
10 V
-5 °C (23 °F)
Parameter 6-11 Terminal
35 °C (95 °F)
53 High Voltage
Parameter 6-24 Terminal
[2] analog input 54
54 Low Ref./Feedb.
Value
Parameter 6-25 Terminal
54 High Ref./Feedb.
ValueParameter 7-20 Pr
ocess CL Feedback 1
Resource
Parameter 7-30 Process
[0] Normal
PID Normal/ Inverse
Control
Parameter 7-31 Process
[1] On
PID Anti Windup
Parameter 7-32 Process
300 RPM
PID Start Speed
Parameter 0-50 LCP
[1] All to LCP
Copy
NOTICE
If necessary, start/stop can be activated several times to
provoke a variation of the feedback signal.
16.3 Optimization of PID Controls
Several tuning methods can be used to tune the PID
controls of the frequency converter. One approach is to
use the Ziegler Nichols tuning method.
NOTICE
Do not use the method described in cases where
oscillations created by marginally stable control settings
can damage applications.
The criteria for adjusting the parameters are based on
evaluating the system at the limit of stability rather than
on taking a step response. The proportional gain is
increased until continuous oscillations are observed (as
measured on the feedback), that is, until the system
becomes marginally stable. The corresponding gain (K
called the ultimate gain. The period of the oscillation (P
(called the ultimate period) is determined as shown in
Illustration 16.5.
Danfoss A/S © 6/2016 All rights reserved.
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MG37N102
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