Introduction To Vlt ® Micro Drive; Control Structures - Danfoss VLT Micro Drive FC 51 Design Manual

Introduction to VLT® Micro ...
3 Introduction to VLT
3 3

3.1 Control Structures

In 1-00 Configuration Mode it can be selected if open or
closed loop is to be used.
3.1.1 Control Structure Open Loop
Reference
handling
Remote
reference
Auto mode
Hand mode
Local
reference
scaled to
Hz
LCP Hand on,
off and auto
on keys
Illustration 3.1 Open Loop Structure
In the configuration shown in Illustration 3.1, 1-00 Configu-
ration Mode is set to [0] Open loop. The resulting reference
from the reference handling system or the local reference
is received and fed through the ramp limitation and speed
limitation before being sent to the motor control. The
output from the motor control is then limited by the
maximum frequency limit.
3.1.2 Local (Hand On) and Remote (Auto
On) Control
The frequency converter can be operated manually via the
local control panel (LCP) or remotely via analog/digital
inputs or serial bus. If allowed in 0-40 [Hand on] Key on
LCP, 0-44 [Off/Reset] Key on LCP, and 0-42 [Auto on] Key on
LCP, it is possible to start and stop the frequency converter
by LCP using the [Hand On] and [Off/Reset] keys. Alarms
can be reset via the [Off/Reset] key. After pressing the
[Hand On] key, the frequency converter goes into Hand
Mode and follows (as default) the local reference set by
using the LCP potentiometer (LCP 12) or [
The potentiometer can be disabled by parameter P6-80. If
potentiometer is disabled, arrow keys can be used for
adjusting reference.
After pressing the [Auto On] key, the frequency converter
goes into Auto mode and follows (as default) the remote
18
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®
VLT Micro Drive FC 51 Design Guide
®
Micro Drive
P 4-14
Motor speed
high limit [Hz]
Remote
Reference
Local
P 4-12
Motor speed
low limit [Hz]
▲ ▼
]/[ ] (LCP 11).
®
MG02K202 - VLT is a registered Danfoss trademark
100%
P 3-4* Ramp 1
P 3-5* Ramp 2
0%
Ramp
100%
-100%
reference. In this mode, it is possible to control the
frequency converter via the digital inputs and RS-485. See
more about starting, stopping, changing ramps and
parameter set-ups etc. in parameter group 5-1* (Digital
Inputs) or parameter group 8-5* (Serial Communication).
Hand Off
On Reset
Illustration 3.2
Local reference forces the configuration mode to open
loop, independent on the setting of 1-00 Configuration
Mode.
Local Reference is restored at power-down.
3.1.3 Control Structure Closed Loop
The internal controller allows the frequency converter to
become an integral part of the controlled system. The
frequency converter receives a feedback signal from a
sensor in the system. It then compares this feedback to a
set-point reference value and determines the error, if any,
To motor
control
P 4-10
Motor speed
direction
Auto
On