A Graphical Local Control Panel (LCP) must be used in order to react on messages during the auto-tuning sequence.
Enabling par. 20-79
PID Autotuning
, puts the frequency converter into auto-tuning mode. The LCP then directs the user with on-screen instructions.
The fan/pump is started by pressing [Auto On] button on the LCP and applying a start signal. The speed is adjusted manually by pressing the [
Ⴃ
] or
[
Ⴍ
] navigation keys on the LCP to a level where the feedback is around the system set-point.
NB!
It is not possible to run the motor at maximum or minimum speed, when manually adjusting the motor speed due to the need of giving
the motor a step in the speed during auto-tuning.
PID auto-tuning functions by introducing step changes whilst operating at a steady state and then monitoring the feedback. From the feedback response,
the required values for par. 20-93
PID Proportional Gain
and par. 20-94
PID Integral Time
are calculated. par. 20-95
PID Differentiation Time
is set to
value 0 (zero). par. 20-81
PID Normal/ Inverse Control
is determined during tuning process.
These calculated values are presented on the LCP and the user can decide whether to accept or reject them. Once accepted, the values are written to
the relevant parameters and auto-tuning mode is disabled in par. 20-79
PID Autotuning
. Depending on the system being controlled the time required to
carry out auto-tuning could be several minutes.
It is advised to set the ramp times in par. 3-41
Ramp 1 Ramp Up Time
, par. 3-42
Ramp 1 Ramp Down Time
or par. 3-51
Ramp 2 Ramp Up Time
and
par. 3-52
Ramp 2 Ramp Down Time
according to the load inertia before carrying out PID autotuning. If PID autotuning is carried out with slow ramp
times, the auto-tuned parameters will typically result in very slow control. Excessive feedback sensor noise should be removed using the input filter
(parameter groups 6-**, 5-5* and 26-**, Terminal 53/54 Filter Time Constant/Pulse Filter Time Constant #29/33) before activating PID autotuning. In
order to obtain the most accurate controller parameters, it is advised to carry out PID autotuning, when the application is running in typical operation,
i.e. with a typical load.
20-70 Closed Loop Type
Option:
Function:
This parameter defines the application response. The default mode should be sufficient for most
applications. If the application response speed is known, it can be selected here. This will decrease
the time needed for carrying out PID autotuning. The setting has no impact on the value of the
tuned parameters and is used only for the autotuning sequence.
[0] *
Auto
[1]
Fast Pressure
[2]
Slow Pressure
[3]
Fast Temperature
[4]
Slow Temperature
20-79 PID Autotuning
Option:
Function:
Select the relative response speed for the application.
[0] *
Disabled
[1]
Enabled
VLT
p
Automation VT Drive FC322
Programming Guide
2 Parameter Description
MG.20.W1.22 - VLT
p
is a registered Danfoss trademark
193
2
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