Local (Hand On) And Remote (Auto On) Control - Danfoss VLT Refrigeration Drive FC 103 Design Manual

Product Overview
information to the frequency converter as a feedback
signal. If the feedback signal exceeds the setpoint
2 2 reference, the frequency converter ramps down to reduce
the pressure. Similarly, if the pipe pressure is lower than
the setpoint reference, the frequency converter ramps up
to increase the pump pressure.
While the default values for the frequency converter in
closed loop often provide satisfactory performance, system
control can often be optimised by tuning the PID
parameters. Auto tuning is provided for this optimisation.
Other programmable features include:
•
Inverse regulation - motor speed increases when
a feedback signal is high. This is useful in
compressor applications, where speed needs to
be increased if the pressure/temperarure is too
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.
2.4.3 Local (Hand On) and Remote (Auto
On) Control
Operate the frequency converter manually via the LCP, or
remotely via analog and digital inputs, and serial bus.
Active reference and configuration mode
The active reference is either a local reference or a remote
reference. Remote reference is the default setting.
•
To use the local reference, configure in Hand
mode. To enable Hand mode, adapt parameter
settings in parameter group 0–4* LCP Keypad. For
more information, refer to the programming
guide.
•
To use the remote reference, configure in Auto
mode, which is the default mode. In Auto mode,
it is possible to control the frequency converter
via the digital inputs and various serial interfaces
(RS485, USB, or an optional fieldbus).
•
Illustration 2.10 shows the configuration mode
resulting from active reference selection, either
local or remote.
•
Illustration 2.11 shows manual configuration mode
for local reference.
20
®
VLT Refrigeration Drive FC 103
Remote
reference
Local
reference
Illustration 2.10 Active Reference
Illustration 2.11 Manual Configuration Mode
Application control principle
Either the remote reference or the local reference is active
at any time. Both cannot be active simultaneously. Set the
application control principle (that is, open loop or closed
loop) in parameter 1-00 Configuration Mode, as shown in
Table 2.3.
When the local reference is active, set the application
control principle in parameter 1-05 Local Mode Configu-
ration.
Set the reference site in parameter 3-13 Reference Site, as
shown in Table 2.3.
For more information, refer to the programming guide.
Danfoss A/S © 08/2015 All rights reserved.
Remote
Auto mode
Linked to hand/auto
Hand mode
Local
LCP Hand on,
o and auto
on keys
P 1-00
Con guration
mode
open loop
Local
reference
closed loop
Reference
P 3-13
Reference site
Scale to
RPM or
Hz
Local
ref.
Scale to
closed loop
unit
MG16G202