Danfoss VLT Refrigeration Drive FC 103 Programming Manual page 136

Parameter Description
NOTICE
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.
3 3
PID auto-tuning introduces step changes while operating
at a steady state and then monitors the feedback. From
the feedback response, the required values for
parameter 20-93 PID Proportional Gain and
parameter 20-94 PID Integral Time are calculated.
Parameter 20-95 PID Differentiation Time is set to value 0
(zero). Parameter 20-81 PID Normal/ Inverse Control is
determined during the tuning process.
These calculated values are presented in the LCP and can
be either accepted or rejected. Once accepted, the values
are written to the relevant parameters and auto-tuning
mode is disabled in parameter 20-79 PID Autotuning.
Depending on the system, the time required to carry out
auto-tuning could be several minutes.
Before carrying out the PID auto-tuning, set the following
parameters according to the load inertia:
•
Parameter 3-41 Ramp 1 Ramp Up Time.
•
Parameter 3-42 Ramp 1 Ramp Down Time.
or
•
Parameter 3-51 Ramp 2 Ramp Up Time.
•
Parameter 3-52 Ramp 2 Ramp Down Time.
If PID auto-tuning is carried out with slow ramp times, the
auto-tuned parameters typically result in very slow control.
Before activating PID auto-tuning, remove excessive
feedback sensor noise using the input filter (parameter
groups 6-** Analog In/Out, 5-5* Pulse Input and 26-** Analog
I/O Option MCB 109, parameter 6-16 Terminal 53 Filter Time
Constant, parameter 6-26 Terminal 54 Filter Time Constant,
parameter 5-54 Pulse Filter Time Constant #29,
parameter 5-59 Pulse Filter Time Constant #33) before
activating PID auto-tuning. To obtain the most accurate
controller parameters, carry out PID auto-tuning when the
application runs in typical operation, that is with a typical
load.
20-70 Closed Loop Type
Option:
[0] Auto
*
134
®
VLT Refrigeration Drive FC 103
Function:
Select the application response speed if it
is known. The default setting is sufficient
for most applications. A more precise
value decreases the time needed for
carrying out PID adaptation. The setting
has no impact on values of parameters
and only affects the auto-tuning speed.
Takes 30–60 s to complete.
Danfoss A/S © 05/2016 All rights reserved.
20-70 Closed Loop Type
Option: Function:
[1] Fast Pressure Takes 10–20 s to complete.
[2] Slow Pressure Takes 30–60 s to complete.
[3] Fast Takes 10–20 minutes to complete.
Temperature
[4] Slow Takes 30–60 minutes to complete.
Temperature
20-71 PID Performance
Option: Function:
[0] Normal Normal setting of this parameter is suitable for
*
pressure control in fan systems.
[1] Fast Fast setting is used in pumping systems, where a
faster control response is wanted.
20-72 PID Output Change
Range: Function:
0.10 [0.01 This parameter sets the magnitude of step
*
- 0.50] change during auto-tuning. The value is a
percentage of full speed. That is, if maximum
output frequency in parameter 4-13 Motor Speed
High Limit [RPM]/parameter 4-14 Motor Speed High
Limit [Hz] is set to 50 Hz, 0.10 is 10% of 50 Hz,
which is 5 Hz. Set this parameter to a value
resulting in feedback changes of 10–20% for best
tuning accuracy.
20-73 Minimum Feedback Level
Range:
-999999 [ -999999.999 -
ProcessCtrlUnit par. 20-74
*
ProcessCtrlUnit]
20-74 Maximum Feedback Level
Range:
999999 [ par. 20-73 -
ProcessCtrlUnit 999999.999
*
ProcessCtrlUnit]
Function:
Enter the minimum allowable
feedback level in user units as
defined in
parameter 20-12 Reference/
Feedback Unit. If the level
drops below
parameter 20-73 Minimum
Feedback Level, auto-tuning is
aborted and an error message
appears in the LCP.
Function:
Enter the maximum allowable
feedback level in user units as
defined in
parameter 20-12 Reference/
Feedback Unit. If the level
rises above
parameter 20-74 Maximum
Feedback Level, auto-tuning is
aborted and an error message
appears in the LCP.
MG16H202