Rs485 Installation And Set-Up; Overview; Network Connection; Frequency Converter Hardware Set-Up - Danfoss VLT Micro Drive FC 51 Design Manual

RS485 Installation and Set-...

8 RS485 Installation and Set-up

8.1 RS485 Installation and Set-up

8.1.1 Overview

RS485 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 1 network segment.
Repeaters divide network segments.
NOTICE
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 shielded
twisted pair (STP) cable for bus cabling, and always follow
good common installation practice.
Low-impedance ground connection of the shield at every
node is important, including at high frequencies. Thus,
connect a large surface of the shield to ground, for
example with a cable clamp or a conductive cable gland. It
may be necessary to apply potential equalizing cables to
maintain the same ground potential throughout the
network, particularly 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
shielded motor cable.
Cable Shielded twisted pair (STP)
Impedance 120
[Ω]
Cable length Maximum 1200 (3937) (including drop lines)
[m (ft)] Maximum 500 (1640) station-to-station
Table 8.1 Cable Specifications

8.1.2 Network Connection

Connect the frequency converter to the RS485 network as
follows (see also Illustration 8.1):
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 shield to the cable clamps.
MG02K402
Design Guide
NOTICE
To reduce noise between conductors, use shielded,
twisted-pair cables.
Illustration 8.1 Network Connection

8.1.3 Frequency Converter Hardware Set-up

To terminate the RS485 bus, use the terminator DIP switch
on the main control board of the frequency converter.
Illustration 8.2 Terminator Switch Factory Setting
The factory setting for the DIP switch is OFF.
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