VLT
®
4000 VT
Programming
■
Reference handling
Reference handling is shown in the block
diagram underneath.
The block diagram shows how a change in a parameter
can affect the resulting reference.
Parameters 203 to 205
Reference handling, minimum
and maximum
reference and parameter 210
Reference
type
define the way reference handling can be
carried out. The mentioned parameters are active
both in a closed and in an open loop.
Remote references are defined as:
•
External references, such as analog inputs 53, 54
and 60, pulse reference via terminal 17/29 and
reference from serial communication.
•
Preset references.
The resulting reference can be shown in the display
by selecting
Reference
[%] in parameters 007-010
Display readout
and in the form of a unit by selecting
Resulting reference [unit]. See the section on
Feedback
handling
in connection with a closed loop.
The sum of the external references can be shown
in the display as a percentage of the range from
Minimum reference, Ref
MIN
to
Maximum reference, Ref
MAX
. Select
External reference
, % [25] in parameters
007-010
Display readout
if a readout is required.
It is possible to have both preset references and
external references at the same time. In parameter 210
Reference type a choice is made of how the preset
references are to be added to the external references.
Furthermore, an independent local reference exists,
where the resulting reference is set by means of
the [+/-] keys. If local reference has been selected,
the output frequency range is limited by parameter
201
Output frequency low limit, f
MIN
and parameter
202
Output frequency high limit, f
MAX
.
NOTE
If the local reference is active, the VLT AFD will
always be in
Open loop
[0], regardless of the
choice made in parameter 100
Configuration
.
The unit of the local reference can be set either as Hz
or as a percentage of the output frequency range. The
unit is selected in parameter 011
Unit of local reference
.
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