12.2 Network Connection
One or more frequency converters can be connected to a
control (or master) using the RS-485 standardised interface.
Terminal 68 is connected to the P signal (TX+, RX+), while
terminal 69 is connected to the N signal (TX-,RX-). See
drawings in
.
If more than one frequency converter is connected to a
master, use parallel connections.
130BA060.11
68 69
68 69
68 69
RS 485
RS 232
USB
+
-
Illustration 12.2 Parallel Connections
To avoid potential equalising currents in the screen,
ground the cable screen via terminal 61, which is
connected to the frame via an RC-link.
130BB021.10
12 13 18 19 27 29 32 33 20 37
Remove jumper to enable Safe Stop
61 68 69
39 42 50 53 54 55
Illustration 12.3 Control Card Terminals
12.3 Bus Termination
The RS-485 bus must be terminated by a resistor network
at both ends. For this purpose, set switch S801 on the
control card for "ON".
Communication protocol must be set to
8-30 Protocol
.
12.4 RS-485 Installation and Set-up
12.4.1 EMC Precautions
The following EMC precautions are recommended to
achieve interference-free operation of the RS-485 network.
Observe relevant national and local regulations, for
example regarding protective earth connection. Keep the
RS-485 communication cable away from motor and brake
resistor cables to avoid coupling of high frequency noise
from one cable to another. Normally, a distance of 200 mm
(8 inches) is sufficient, but keeping the greatest possible
distance between the cables is recommended, especially
where cables run in parallel over long distances. When
crossing is unavoidable, the RS-485 cable must cross motor
and brake resistor cables at an angle of 90
°
.
Fieldbus cable
Min. 200 mm
90° crossing
Brake resistor
130BD507.11
Illustration 12.4 Cable Routing
12.5 FC Protocol Overview
The FC protocol, also referred to as FC bus or Standard
bus, is the Danfoss standard fieldbus. It defines an access
technique according to the master-follower principle for
communications via a serial bus.
One master and a maximum of 126 followers can be
connected to the bus. The master selects the individual
followers via an address character in the telegram. A
follower itself can never transmit without first being
requested to do so, and direct message transfer between
the individual followers is not possible. Communications
occur in the half-duplex mode.
RS-485 Installation and Set...
VLT
®
AutomationDrive FC 301/FC 302 Design Guide, 0.25-75 kW
MG33BF02 - Rev. 2013-12-20
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