Network Connection; Bus Termination; Installation And Set-Up; Fc Protocol Overview - Danfoss VLT AutomationDrive FC 301 Design Manual

RS-485 Installation and Set...

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 chapter 3.5 Wiring Schematic.
If more than one frequency converter is connected to a
master, use parallel connections.
RS 232
USB
RS 485
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.
61 68 69
Remove jumper to enable Safe Stop
12 13 18 19
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.
®
VLT AutomationDrive FC 301/FC 302 Design Guide, 0.25-75 kW
68 69 68 69 68 69
+
-
39 42 50 53 54 55
27 29 32 33 20 37
MG33BF02 - Rev. 2013-12-20
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°.
Min. 200 mm
90° crossing
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.
12
Brake resistor
177
12