Feedback Handling - Danfoss VLT AQUA Drive FC 202 Design Manual

Product Overview

2.4.5 Feedback Handling

Feedback handling can be configured to work with
applications requiring advanced control, such as multiple
setpoints and multiple types of feedback (see Figure 2.16.
Three types of control are common:
Single zone, single setpoint
This control type is a basic feedback configuration.
Setpoint 1 is added to any other reference (if any) and the
feedback signal is selected.
Multi-zone, single setpoint
This control type uses two or three feedback sensors but
only one setpoint. The feedback can be added, subtracted,
or averaged. In addition, the maximum or minimum value
can be used. Setpoint 1 is used exclusively in this configu-
ration.
Figure 2.16 Block Diagram of Feedback Signal Processing
MG20N622
Design Guide
Multi-zone, setpoint/feedback
The setpoint/feedback pair with the largest difference
controls the speed of the adjustable frequency drive. The
maximum attempts to keep all zones at or below their
respective setpoints, while minimum attempts to keep all
zones at or above their respective setpoints.
Example
A 2-zone, 2-setpoint application. Zone 1 setpoint is 15 bar
and the feedback is 5.5 bar. Zone 2 setpoint is 4.4 bar and
the feedback is 4.6 bar. If maximum is selected, the zone 1
setpoint and feedback are sent to the PID controller, since
it has the smaller difference (feedback is higher than
setpoint, resulting in a negative difference). If minimum is
selected, the zone 2 setpoint and feedback is sent to the
PID controller, since it has the larger difference (feedback is
lower than setpoint, resulting in a positive difference).
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