RS-485 is a two-wire bus interface compatible with multi-drop network topology, i.e., 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 up by repeaters. Please note that 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 adjustable frequency drives 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 very important, also at high frequencies. This can be achieved by connecting a large

surface of the shield to ground, by means of a cable clamp or a conductive cable gland, for example. It may be necessary to apply potential-equalizing

cables to maintain the same ground potential throughout the network, particularly in installations where there are long lengths of cable.

To prevent impedance mismatch, always use the same type of cable throughout the entire network. When connecting a motor to the adjustable frequency

drive, always use shielded motor cable.

Cable: Shielded twisted pair (STP)

Impedance: 120 Ohm

Cable length: Max. 3,396 ft [1,200 m] (including drop lines)

Max. 1,640 ft [500 m] station-to-station

MG.20.N5.22 - VLT

is a registered Danfoss trademark

7 RS-485 Installation and Set-up

7-1

Table of Contents