Illustration 3.15 Location of Bus Termination Switch
To run STO, additional wiring for the frequency converter
is required. Refer to VLT
®
Frequency Converters Safe Torque
Off Operating Instructions for further information.
3.6
Serial Communication
RS485 is a two-wire bus interface compatible with multi-
drop network topology.
Terminate each segment at both ends, using the
termination switch (S801) of the frequency converter.
Always use screened twisted pair (STP) cable for bus
cabling, and always follow good common installation
practice.
Low-impedance earth (ground) connection of the screen at
every node is important, including at high frequencies.
Thus, connect a large surface of the screen to earth
(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 earth (ground)
potential throughout the network. Particularly in instal-
lations with long cables.
Cable Screened twisted pair (STP)
Impedance
120 Ω
Max. cable length
1200 m (including drop lines)
500 m station-to-station
Table 3.6
Installation Danfoss Turbocor
16 Danfoss A/S © 01/2015 All rights reserved. MG35Q202
33
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