Installation And Set-Up; Rs-485; Overview; Network Connection - Danfoss FC 101 Design Manual

RS-485 Installation and Set...
7 RS-485 Installation and Set-up

7.1 RS-485

7.1.1 Overview

RS-485 is a 2-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.
NOTICE
Each repeater functions as a node within the segment in
7 7 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
Impedance
[Ω]
Cable length
[m]
Table 7.1 Cable

7.1.2 Network Connection

Connect the frequency converter to the RS-485 network
as follows (see also Illustration 7.1):
1. Connect signal wires to terminal 68 (P+) and
terminal 69 (N-) on the main control board of the
frequency converter.
2. Connect the cable screen to the cable clamps.
80
Screened twisted pair (STP)
120
Max. 1200 (including drop lines)
Max. 500 station-to-station
®
VLT HVAC Basic Drive FC 101 Design Guide
NOTICE
Screened, twisted-pair cables are recommended
to reduce noise between conductors.
Illustration 7.1 Network Connection
7.1.3 Frequency Converter Hardware Set-
up
Use the terminator dip switch on the main control board
of the frequency converter to terminate the RS-485 bus.
Illustration 7.2 Terminator Switch Factory Setting
The factory setting for the dip switch is OFF.
MG18C502 - Rev. 2013-09-06
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