Rs485 Installation And Set-Up; Installation And Set-Up - Danfoss VLT AAF006 Operating Instructions Manual

RS485 Installation and Set-...

7 RS485 Installation and Set-up

7.1 Installation and Set-up

7.1.1 Overview
RS485 is a 2-wire bus interface compatible with multi-drop
network topology. 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.
Network segments are divided by repeaters. 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 unit, or a biased
termination resistor network. Use screened twisted pair
(STP) cable for bus cabling, and follow good common
installation practice.
Low-impedance ground connection of the screen at every
node is very important, including at high frequencies. This
can be achieved by connecting a large surface of the
screen-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 instal-
lations where there are long lengths of cable.
To prevent impedance mismatch, use the same type of
cable throughout the entire network.
Cable Screened twisted pair (STP)
Impedance 120 Ω
Cable length Maximum 1200 m (3937 ft.), including drop lines
Maximum 500 m (1640 ft.) station-to-station
Table 7.1 Cable Specifications
MG90V302
Operating Instructions
7.1.2 Network Connection
Connect the unit to the RS485 network as follows:
1.
2.
NOTICE
Screened, twisted-pair cables are recommended to
reduce noise between conductors.
61 68 69
Illustration 7.1 Control Card Terminals
Danfoss A/S © 09/2014 All rights reserved.
Connect signal wires to terminal 68 (P+) and
terminal 69 (N-) on the main control board of the
unit.
Connect the cable screen to the cable clamps.
39 42 50 53 54 55
Remove jumper to enable Safe Stop
12 13 18 19 27 29 32
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33 20 37
69
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