Danfoss VLT AutomationDrive FC 300 Series - 10 Installation and Set-Up; Overview; Network Connection; Bus Termination

10 RS-485 Installation and Set-up
10.1 Installation and Set-up
10.1.1 Overview
RS-485 is a two-wire bus interface compatible with multi-
drop network topology, that is, nodes can be connected as
a bus, or via drop cables from a common trunk line. A
total of 32 nodes can be connected to one network
segment.
Repeaters divide network segments.
NOTE
Each repeater functions as a node within the segment in
which it is installed. Each node connected within a given
network must have a unique node address, across all
segments.
Terminate each segment at both ends, using either the
termination switch (S801) of the frequency converters or a
biased termination resistor network. Always use screened
twisted pair (STP) cable for bus cabling, and always follow
good common installation practice.
Low-impedance earth connection of the screen at every
node is important, including at high frequencies. Thus,
connect a large surface of the screen to earth, for example
with a cable clamp or a conductive cable gland. It may be
necessary to apply potential-equalizing cables to maintain
the same earth potential throughout the network - partic-
ularly in installations with long cables.
To prevent impedance mismatch, always use the same
type of cable throughout the entire network. When
connecting a motor to the frequency converter, always use
screened motor cable.
Cable
Screened twisted pair (STP)
Impedance
120 Ω
Cable length
Max. 1200 m (including drop lines)
Max. 500 m station-to-station
Table 10.1 Cable
10.2
Network Connection
One or more frequency converters can be connected to a
control (or master) using the RS-485 standardized 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 7.8.3 Earthing of Screened Control Cables.
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 10.1 Parallel Connections
In order to avoid potential equalizing currents in the
screen, earth 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 10.2 Control Card Terminals
10.3 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".
For more information, see 7.5.4 Switches S201, S202, and
S801 .
Communication protocol must be set to 8-30 Protocol.
RS-485 Installation and Set...
VLT
®
AutomationDrive FC 300 Design Guide, 0.25-75 kW
MG33BE02 - VLT
®
is a registered Danfoss trademark 181
10
10
RSPSupply - 1-888-532-2706 - www.RSPSupply.com
http://www.RSPSupply.com/p-21462-Danfoss-131B8966-VLT-Automation-VT-Drive-VFD-FC301-230V-5-HP.aspx