Control Structure Closed Loop (Pi); Local [Hand On] And Remote [Auto On] Control - Danfoss VLT DriveMotor FCP 106 Design Manual

Product Overview

2.3.2 Control Structure Closed Loop (PI)

The internal controller allows the drive to become a part of the controlled system. The drive receives a feedback signal from
a sensor in the system. It then compares this feedback to a setpoint reference value and determines the difference, if any,
between these 2 signals. It then adjusts the speed of the motor to correct this difference.
For example, consider a pump application controlling the speed of a pump to ensure a constant static pressure in a pipe.
The desired static pressure value is supplied to the drive as the setpoint reference. A static pressure sensor measures the
actual static pressure in the pipe and supplies this data to the drive as a feedback signal. If the feedback signal is greater
than the setpoint reference, the drive reduces speed to reduce the pressure. In a similar way, if the pipe pressure is lower
than the setpoint reference, the drive automatically speeds up to increase the pump pressure.
+
S
Reference
-
Feedback
Illustration 2.14 Closed-loop Controller
While the default values for the closed-loop controller often provide satisfactory performance, the control of the system can
often be optimized by adjusting the closed-loop controller parameters.

2.4 Local [Hand On] and Remote [Auto On] Control

Operate the drive manually via the local control panel
(LCP) or remotely via analog/digital inputs or fieldbus.
Start and stop the drive pressing the [Hand On] and [Off/
Reset] keys on the LCP. Set-up is required:
•
Parameter 0-40 [Hand on] Key on LCP.
•
Parameter 0-44 [Off/Reset] Key on LCP.
•
Parameter 0-42 [Auto on] Key on LCP.
Reset alarms via the [Off/Reset] key or via a digital input,
when the terminal is programmed to Reset.
Hand
Off
On
Illustration 2.15 LCP Control Keys
Local reference forces the configuration mode to open
loop, independent of the setting in parameter 1-00 Configu-
ration Mode.
MG03M302
Design Guide
PI
*[-1]
20-81 PI
Normal/Inverse
control
Auto
Reset
On
Danfoss A/S © 12/2018 All rights reserved.
100%
0%
Scale to
speed
100%
-100%
P 4-10
Motor speed
direction
Local reference is restored at power-down.
2
To motor
control
P 4-19
Max output
frequency (Hz)
17
2