Operating instructions

VLT
®
2800, VLT
®
6000 HVAC and VLT
®
8000 AQUA Modbus RTU
Parameter
Handling
■ Serial communication reference
The serial communication reference is transferred to
the frequency converter as a 16-bit word. The value is
transferred in whole numbers 0 - ±32767 (±200%).
16384 (4000 Hex) corresponds to 100%.
The serial communication reference has the following
format: 0-16384 (4000 Hex)
0-100% (Par. 204
Minimum ref. - Par. 205 Maximum ref.).
It is possible to change the direction of rotation via the
serial reference. This is done by converting the binary
reference value to 2’ complement. See example.
E
xample - Control word and serial communication ref.:
The frequency converter is to receive a start
command and the reference is to be set to 50%
(2000 Hex) of the reference range.
Control word = 047F Hex ⇒ Start command.
Reference = 2000 Hex ⇒ 50% reference.
The frequency converter is to receive a start
command and the reference is to be set to -50%
(-2000 Hex) of the reference range.
The reference value is first converted to 1’ complement,
and then 1 is added binarily to obtain 2’ complement:
2000 Hex 0010 0000 0000 0000 0000
1’ complement 1101 1111 1111 1111 1111
+1
2’ complement 1110 0000 0000 0000 0000
Control word = 047F Hex ⇒ Start command.
Reference = E000 Hex ⇒ -50% reference.
■ Present output frequency
The value of the frequency converter’s present output
frequency is transferred as a 16-bit word. The value is
transferred as whole numbers 0 - ±32767 (±200%).
16384 (4000 Hex) corresponds to 100%.
Output frequency has the following format:
0-16384 (4000 Hex)
0-100% (Par. 201
Output frequency low limit - Par. 202 Output
frequency high limit).
E
xample - Status word and current output frequency:
The master receives a status message from the
frequency converter that the current output frequency
is 50% of the output frequency range.
Par. 201 Output frequency low limit =0Hz
Par. 202 Output frequency high limit =50Hz
Status word = 0F03 Hex.
Output frequency = 2000 Hex ⇒ 50% of the frequency
range, corresponding to 25 Hz.
■ Control Word Bit Descriptions VLT 6000 / VLT 8000
The control word is used for transmitting commands
from a master (e.g. a PC) to a slave.
MG.10.S2.02 - VLT is a registered Danfoss trademark
23