Danfoss VLT AutomationDrive FC 302 Design Manual page 183

Basic Operating Principles ...
Ref.
+
Handling

(Illustra-
tion)
_
Feedback
Handling
(Illustra-
tion)
Illustration 11.7 Block Diagram of Closed-loop Controller
Programmable features
While the default values for the drive in closed loop often provide satisfactory performance, system control can often be
optimized by tuning the PID parameters. Auto tuning is provided for this optimization.
•
Inverse regulation - motor speed increases when a feedback signal is high.
•
Start-up frequency - lets the system quickly reach an operating status before the PID controller takes over.
•
Built-in lowpass filter - reduces feedback signal noise.
11.2.7 Control Processing
See Active/Inactive Parameters in Different Drive Control Modes in the programming guide for an overview of which control
configuration is available for your application, depending on selection of AC motor or PM non-salient motor.
11.2.7.1 Control Structure in VVC
P 1-00
Con g. mode
Ref.
+
Process

_
P 7-20 Process feedback
1 source
P 7-22 Process feedback
2 source
Illustration 11.8 Control Structure in VVC
In Illustration 11.8, the resulting reference from the reference handling system is received and fed through the ramp
limitation and speed limitation before being sent to the motor control. The output of the motor control is then limited by
the maximum frequency limit.
MG38C202
Design Guide
PID
*[-1]
P 20-81
PID Normal/Inverse
Control
+
P 4-13
Motor speed
high limit (RPM)
P 1-00
P 4-14
Con g. mode
Motor speed
high limit (Hz)
P 3-**
High
Ramp
Low
P 4-11
Motor speed
low limit (RPM)
P 4-12
Motor speed
low limit (Hz)
+
Open Loop and Closed-loop Configurations
Danfoss A/S © 01/2018 All rights reserved.
100%
0%
100%
-100%
P 4-10
Motor speed
direction
P 4-19
Max. output freq.
+f max.
Motor
controller
-f max.
P 7-0*
Speed Motor
+

PID controller
_
P 7-00 Speed PID
feedback source
To motor
Scale to
control
speed
11
P 4-19
Max. output freq.
+f max.
-f max.
181
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