Danfoss VLT HVAC Series Programming Manual page 202

3 Parameter Description
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 autotuning.
PID autotuning functions by introducing step changes while operating at a steady state and then monitoring the feedback. From the feedback response,
the required values for par.20-93
0 (zero). par.20-81 PID Normal/ Inverse Control
3
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 autotuning mode is disabled in par.20-79
carry out autotuning could be several minutes.
It is advised to set the ramp times in par.3-41
Ramp 2 Ramp-down Time
3-52
the autotuned 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:
[0] * Auto
[1] Fast Pressure
[2] Slow Pressure
[3] Fast Temperature
[4] Slow Temperature
20-71 Tuning Mode
Option:
[0] * Normal
[1] Fast
20-72 PID Output Change
Range:
0.10 N/A* [0.01 - 0.50 N/A]
3-178
PID Proportional Gain and par.20-94
is determined during tuning process.
Ramp 1 Ramp-up Time
according to the load inertia before carrying out PID autotuning. If PID autotuning is carried out with slow ramp times,
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.
Function:
Normal setting of this parameter will be suitable for pressure control in fan systems.
Fast setting would generally be used in pumping systems, where a faster control response is de-
sirable.
Function:
This parameter sets the magnitude of step change during autotuning. The value is a percentage of
full speed. This means that if the maximum output frequency inpar.4-13
[RPM]
/par.4-14
This parameter should be set to a value resulting in feedback changes of between 10% and 20%
for best tuning accuracy.
MG.11.C6.22 - VLT
PID Integral Time are calculated. par.20-95
PID Auto Tuning . Depending on the system being controlled, the time required to
Ramp 1 Ramp-down Time
, par.3-42
Motor Speed High Limit [Hz]
is set to 50 Hz, 0.10 is 10% of 50 Hz, which is 5 Hz.
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VLT ® HVAC Drive Programming Guide
PID Differentiation Time is set to value
Ramp 2 Ramp-up Time
or par.3-51
Motor Speed High Limit
and par.