NOTE
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
and
are calculated.
20-95 PID Differentiation Time
is set to value
0 (zero).
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 meters and
auto-tuning mode is disabled in
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
or
and
according to
the load inertia before carrying out PID autotuning. If PID
autotuning is carried out with slow ramp times, the auto-
tuned meters will typically result in very slow control.
Excessive feedback sensor noise should be removed using
the input filter (meter 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 meters, 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 meter 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 meters and is
used only for the autotuning sequence.
[0]
*
Auto
[1]
Fast Pressure
[2]
Slow Pressure
[3]
Fast Temperature
[4]
Slow Temperature
20-71 PID Performance
Option:
Function:
[0]
*
Normal Normal setting of this meter will be suitable for
pressure control in fan systems.
20-71 PID Performance
Option:
Function:
[1]
Fast
Fast setting would generally be used in pumping
systems, where a faster control response is
desirable.
20-72 PID Output Change
Range:
Function:
0.10
*
[0.01 -
0.50 ]
This meter sets the magnitude of step change
during autotuning. The value is a percentage
of full speed. I.e. if maximum output frequency
in
4-13 Motor Speed High Limit [RPM]
4-14 Motor Speed High Limit [Hz]
is set to 50Hz,
0.10 is 10% of 50Hz, which is 5Hz. This meter
should be set to a value resulting in feedback
changes of between 10% and 20% for best
tuning accuracy.
20-73 Minimum Feedback Level
Range:
Function:
-999999.000
ProcessCtrlUnit
*
[ -999999.999 -
par. 20-74
ProcessCtrlUnit]
The minimum allowable
feedback level should be
entered here in User units
as defined in
20-12 Reference/Feedback
Unit
. If the level falls below
, autotuning is
aborted and an error
message will appear on
the LCP.
20-74 Maximum Feedback Level
Range:
Function:
999999.000
ProcessCtrlUnit
*
[ par. 20-73 -
999999.999
ProcessCtrlUnit]
The maximum allowable
feedback level should be
entered here in User units
as defined in
20-12 Reference/Feedback
Unit
. If the level rises
above
, autotuning
is aborted and an error
message will appear on
the LCP.
20-79 PID Autotuning
Option:
Function:
This meter starts the PID autotuning sequence.
Once the autotuning has successfully completed
and the settings have been accepted or rejected
by the user, by pressing [OK] or [Cancel] buttons
on the LCP at the end of tuning, this meter is
reset to [0] Disabled.
[0]
*
Disabled
Parameter Description
VLT
®
HVAC Drive Programming Guide
136
MG.11.CC.02 - VLT
®
is a registered Danfoss trademark
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