455
Frequency range monitor
Value:
Disable
[0]
Enable
[1]
Function:
his parameter is used if warning 35
Out of frequency range
must be
turned off in the display in process control closed loop. This parameter
does not affect the extended status word.
Description of choice:
Select
Enable
[1] to enable the readout in the display if warning 35
Out
of frequency range
occurs. Select
Disable
[0] to disable the readout in
the display if warning 35
ut of frequency range
occurs.
456
Brake Voltage Reduce
Value:
0 - 200 V
0
Function:
The user sets the voltage by which the level for resistor braking is re-
duced. It is only active when resistor in parameter 400 is selected.
Description of choice:
The greater the reduction value, the faster the reaction to a generator
overload. Should only be used if there are problems with overvoltage in
the intermediate circuit.
NB!
A change of selection will not become active until the
mains voltage has been disconnected and reconnec-
ted.
4.7 Serial Communication
4.7.1 Protocols
All frequency converters are equipped with an RS 485 port as standard,
which makes it possible to choose between two protocols. The two pro-
tocols that can be selected in parameter 512
Telegram Profile
, are:
•
Profidrive protocol
•
Danfoss FC protocol
To select Danfoss FC protocol, parameter 512
Telegram Profile
is set to
FC protocol
[1].
4.7.2 Telegram Traffic
Control and response telegrams
Telegram traffic in a master-slave SYSTEM is controlled by the master. A
maximum of 31 slaves can be connected to a master, unless repeaters
are used. If repeaters are used, a maximum of 126 slaves can be con-
nected to a master.
The master constantly sends telegrams addressed to the slaves and waits
for response telegrams from them. The slave's response time is a maxi-
mum of 50 ms.
Only a slave that has received an error-free telegram, addressed to that
slave can send a response telegram.
Broadcast
A master can send the same telegram simultaneously to all slaves con-
nected to the bus. During this broadcast communication the slave does
not send any response telegrams back to the master as to whether the
telegram has been correctly received. Broadcast communication is set up
in address format (ADR), see
Telegram structure
.
Content of a character (byte)
Each character transferred begins with a start bit. Then 8 data bits are
transferred, corresponding to a byte. Each character is secured via a par-
ity bit, which is set at "1" when it reaches parity (i.e. when there is an
equal number of 1's in the 8 data bits and the parity bit in total). A char-
acter is completed by a stop bit, thus consisting of 11 bits in all.
4 Programming
VLT
®
Decentral FCD 300 Design Guide
98
MG.90.S1.02 - VLT
®
is a registered Danfoss trademark
4
