Danfoss VLT AQUA Drive Design Manual page 29

®
VLT AQUA Drive Design Guide
The Remote Reference is comprised of:
• Preset references.
• External references (analog inputs, pulse frequency inputs, digital potentiometer inputs and serial communication bus references).
• The Preset relative reference.
• Feedback controlled setpoint.
Up to 8 preset references can be programmed in the drive. The active preset reference can be selected using digital inputs or the serial communications
bus. The reference can also be supplied externally, most commonly from an analog input. This external source is selected by one of the 3 Reference
Source parameters (par. 3-15 Reference
This is also commonly called a Speed Up/Speed Down Control or a Floating Point Control. To set it up, one digital input is programmed to increase the
reference while another digital input is programmed to decrease the reference. A third digital input can be used to reset the Digipot reference. All reference
resources and the bus reference are added to produce the total External Reference. The External Reference, the Preset Reference or the sum of the two
can be selected to be the active reference. Finally, this reference can by be scaled using par. 3-14 Preset
The scaled reference is calculated as follows:
( )
Y
Reference X X
= + ×
100
Where X is the external reference, the preset reference or the sum of these and Y is par. 3-14 Preset
NB!
If Y, par. 3-14 Preset
2.9.9. Feedback Handling
A block diagram of how the drive processes the feedback signal is shown below.
Feedback handling can be configured to work with applications requiring advanced control, such as multiple setpoints and multiple feedbacks. Three
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 par. 20-20.
Multi Zone, Single Setpoint
Multi Zone Single Setpoint uses two or three 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.
1 Source 2 Source
, par. 3-16 Reference
Relative Reference
is set to 0%, the reference will not be affected by the scaling
®
MG.20.N4.02 - VLT is a registered Danfoss trademark
2. Introduction to VLT AQUA Drive
3 Source
and par. 3-17 Reference ). Digipot is a digital potentiometer.
Relative Reference
Relative Reference
.
in [%].
29
2