Danfoss FC 102 Design Manual page 38

Introduction to VLT® HVAC D...
2 2
Ref.
Handling
(Illustra-
tion)
Feedback
Handling
(Illustra-
tion)
Illustration 2.26 Block Diagram of Closed Loop Controller
While the default values for the frequency converter's closed loop controller often provides satisfactory performance, the
control of the system can often be optimised by adjusting some of the closed loop controller's parameters. It is also
possible to autotune the PI constants.
2.8.7 Feedback Handling
Setpoint 1
P 20-21
Setpoint 2
P 20-22
Setpoint 3
P 20-23
Feedback 1 Source
P 20-00
Feedback 2 Source
P 20-03
Feedback 3 Source
P 20-06
Illustration 2.27 Block Diagram of Feedback Signal Processing
Feedback handling can be configured to work with
applications requiring advanced control, such as multiple
setpoints and multiple feedbacks. 3 types of control are
common.
Single Zone, Single Setpoint
Single Zone, Single Setpoint is a basic configuration.
Setpoint 1 is added to any other reference (if any, see
Reference Handling) and the feedback signal is selected
using 20-20 Feedback Function.
36
Design Guide
+

_
*[-1]
P 20-81
PID Normal/Inverse
Control
Feedback 1
Feedback conv.
P 20-01
Feedback conv. Feedback 2
P 20-04
Feedback conv. Feedback 3
P 20-07
Danfoss A/S © Rev. 06/2014 All rights reserved.
100%
0%
PID
100%
-100%
Motor speed
Multi setpoint min.
Multi setpoint max.
Feedback 1 only
Feedback 2 only
Feedback 3 only
Sum (1+2+3)
Di erence (1-2)
Average (1+2+3)
Minimum (1|2|3)
Maximum (1|2|3)
Multi Zone, Single Setpoint
Multi Zone Single Setpoint uses 2 or 3 feedback sensors,
but only one setpoint. The feedbacks can be added,
subtracted (only feedback 1 and 2) or averaged. In
addition, the maximum or minimum value may be used.
Setpoint 1 is used exclusively in this configuration.
If [13] Multi Setpoint Min is selected, the setpoint/feedback
pair with the largest difference controls the speed of the
frequency converter. [14] Multi Setpoint Maximum attempts
to keep all zones at or below their respective setpoints,
To motor
Scale to
control
speed
P 4-10
direction
Setpoint to
Reference
0%
Handling
0%
0%
Feedback
0%
Feedback Function
P 20-20
MG11BC02