If
Multi Setpoint Min
[13] is selected, the setpoint/feedback pair with the largest difference controls the speed of the drive.
Multi Setpoint Maximum
[14]
attempts to keep all zones at or below their respective setpoints, while
Multi Setpoint Min
[13] attempts to keep all zones at or above their respective
setpoints.
Example:
A two zone two 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
Multi
Setpoint Max
[14] is selected, Zone 1’s setpoint and feedback are sent to the PID controller, since this has the smaller difference (feedback is higher than
setpoint, resulting in a negative difference). If
Multi Setpoint Min
[13] is selected, Zone 2’s setpoint and feedback is sent to the PID controller, since this
has the larger difference (feedback is lower than setpoint, resulting in a positive difference).
2.8.6 Feedback Conversion
In some applications it may be useful to convert the feedback signal. One example of this is using a pressure signal to provide flow feedback. Since the
square root of pressure is proportional to flow, the square root of the pressure signal yields a value proportional to the flow. This is shown below.
2 Introduction to VLT AQUA Drive
VLT
®
AQUA Drive Design Guide
22
MG.20.N5.02 - VLT
®
is a registered Danfoss trademark
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