3.6 Serial Communication
RS-485 is a 2-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 1 network segment.
Repeaters divide network segments. Each repeater
functions as a node within the segment it is installed in.
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 converter or a biased termination
resistor network.
•
Always use screened twisted pair (STP) cable for
bus cabling.
•
Always follow good common installation practice.
Low-impedance ground connection of the screen at every
node is important, including at high frequencies.
•
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-equalizing cables to maintain the same
ground 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
Screened twisted pair (STP)
Impedance
120 Ω
Max. cable length [m] 1200 (including drop lines)
500 station-to-station
Table 3.9 Cable Information
3.7
Optional Equipment
3.7.1 Anti-condensation Heater
An anti-condensation heater can be installed inside the
frequency converter to prevent condensation from forming
inside the enclosure when the unit is turned off. The
heater is controlled by customer-supplied 230 V AC. For
best results, only operate the heater when the unit is not
running.
3.7.2
Mains Shield
The mains shield is a Lexan cover installed inside the
enclosure to provide protection according to BGV A3
(former VBG-4) accident-prevention requirements.
NOTICE
Mains shield is only available for IP21/IP54 (NEMA 1/
NEMA 12).
Installation Operating Instructions
MG16J202 Danfoss A/S © Rev. 05/2014 All rights reserved. 53
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