Danfoss VLT AHF 005 Design Guide

11.2.3 Feedback Handling
Feedback handling can be congured to work with applications requiring advanced control, such as multiple setpoints and
multiple types of feedback. See Illustration 11.4. Three types of control are common:
Single zone (single setpoint)
This control type is a basic feedback conguration. Setpoint 1 is added to any other reference (if any) and the feedback
signal is selected.
Multi-zone (single setpoint)
This control type uses 2 or 3 feedback sensors but only 1 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 conguration.
Multi-zone (setpoint/feedback)
The setpoint/feedback pair with the largest dierence controls the speed of the drive. The maximum value attempts to keep
all zones at or below their respective setpoints, while the minimum value 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 2 setpoint and feedback are sent to the PID controller, since it has the
smaller dierence (feedback is higher than setpoint, resulting in a negative dierence). If minimum is selected, the zone 1
setpoint and feedback is sent to the PID controller, since it has the larger dierence (feedback is lower than setpoint,
resulting in a positive dierence).
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
Feedback conv.
P 20-01
Feedback conv.
P 20-04
Feedback conv.
P 20-07
Feedback 1
Feedback 2
Feedback 3
Feedback
Feedback Function
P 20-20
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)
Setpoint to
Reference
Handling
0%
0%
0%
0%
130BA354.12
Illustration 11.4 Block Diagram of Feedback Signal Processing
Basic Operating Principles ... Design Guide
MG16C302 Danfoss A/S © 11/2017 All rights reserved. 203
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Danfoss VLT AHF 005 Specifications

General

Brand	Danfoss
Model	VLT AHF 005
Category	DC Drives
Language	English