Technical information

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 parameters
and auto-tuning mode is disabled in 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 3-41 Ramp 1 Ramp Up
Time, 3-42 Ramp 1 Ramp Down Time or 3-51 Ramp 2 Ramp
Up Time and 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
20-71 PID Performance
Option: Function:
[0] * Normal Normal setting of this parameter will be suitable
for pressure control in fan systems.
[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 parameter 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
20-72 PID Output Change
Range: Function:
set to 50Hz, 0.10 is 10% of 50Hz, which is 5Hz.
This parameter 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
20-73 Minimum Feedback
Level, 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 20-74 Maximum
Feedback Level, autotuning
is aborted and an error
message will appear on
the LCP.
20-79 PID Autotuning
Option: Function:
This parameter 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 parameter is reset to [0] Disabled.
[0] * Disabled
[1] Enabled
3.18.6 20-8* PID Basic Settings
This parameter group is used to configure the basic
operation of the frequency converter’s PID Controller,
including how it responds to a feedback that is above or
below the setpoint, the speed at which it first starts
functioning, and when it will indicate that the system has
reached the setpoint.
Parameter Description
VLT
®
HVAC Drive Programming Guide
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®
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