Specifications

8 Installation and Set-up
8.1 Installation and Set-up
8.1.1 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
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 ground connection of the screen at every
node is important, including at high frequencies. Thus,
connect 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-equalising cables to
maintain the same earth 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
screened motor cable.
Cable Screened twisted pair (STP)
Impedance
[Ω]
120
Cable length
[m]
Max. 1200 (including drop lines)
Max. 500 station-to-station
Table 8.1 Cable Specifications
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 6.8.3 Grounding 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 8.1 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.
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 8.2 Control Card Terminals
8.1.2
Frequency Converter Hardware Setup
Use the terminator dip switch on the main control board
of the frequency converter to terminate the RS-485 bus.
Installation and Set-up Design Guide
130 Danfoss A/S © Rev. 06/2014 All rights reserved. MG11BC02
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