Danfoss VLT FC 103 Programming Manual page 118

Parameter Description
20-38 Air Density Factor [%]
Range: Function:
100 % [50 - 150 Set the air density factor for conversion
*
%] from pressure to flow in % relative to the
air density at sea level at 20 °C (100% ~
1,2 kg/m
3.15.4 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 with sensorless specific plug in.
20-60 Sensorless Unit
Option:
[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
3.15.5 20-7* PID autotuning
The frequency converter PID Closed Loop controller
(parameter group 20-**, FC Drive Closed Loop) can be
auto-tuned, simplifying and saving time during commis-
sioning, whilst ensuring accurate PID control adjustment.
To use auto-tuning it is necessary for the frequency
®
VLT Refrigeration Drive Programming Guide
3 ).
Function:
®
MG16H102 - VLT is a registered Danfoss trademark
converter to be configured for closed loop in 1-00 Configu-
ration Mode.
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] and
applying a start signal. The speed is adjusted manually by
▲ ▼
pressing [ ] or [ ] 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
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.
3 3
117