Danfoss VLT Programming Manual page 130

Parameter Description
3.18.4 20-6* Sensorless
Parameters for Sensorless. See also 20-00 Feedback 1 Source,
18-50 Sensorless Readout [unit], 16-26 Power Filtered [kW] and
16-27 Power Filtered [hp].
NOTE
Sensorless unit and Sensorless Information requires set up by
MCT10 with sensorless specific plug in.
20-60 Sensorless Unit
Option: Function:
Select the unit to be used with 18-50 Sensorless
Readout [unit].
[20] l/s
[21] l/min
[22] l/h
[23] m³/s
[24] m³/min
[25] m³/h
[70] mbar
[71] bar
[72] Pa
[73] kPa
[74] m WG
[75] mm Hg
[120] GPM
[121] gal/s
[122] gal/min
[123] gal/h
[124] CFM
[125] ft³/s
[126] ft³/min
[127] ft³/h
[170] psi
[171] lb/in²
[172] in WG
[173] ft WG
[174] in Hg
20-69 Sensorless Information
Range:
0 [0 - 0 ]
*
3.18.5 20-7* PID autotuning
The frequency converter PID Closed Loop controller
(parameters 20-**, FCDrive Closed Loop) can be auto-tuned,
simplifying and saving time during commissioning, whilst
ensuring accurate PID control adjustment. To use auto-
tuning it is necessary for the frequency converter to be
configured for closed loop in 1-00 Configuration Mode.
®
VLT HVAC Drive Programming Guide
A Graphical Local Control Panel (LCP) must be used in order
to react on messages during the auto-tuning sequence.
Enabling 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 [
LCP to a level where the feedback is around the system set-
point.
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 20-93 PID Proportional Gain and 20-94 PID Integral Time
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 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
Function:
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.
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