Emc Precautions - Danfoss FC 300 Profibus Manual

FC 300 Profibus
The length statements in the tables above are valid for bus cable with the following properties:
-
Impedance: 135 to 165 ohm at a measuring frequency from 3 to 20 MHz
-
Resistance: <110 ohm/km
-
Capacitance: <30 pF/m
-
Damping: max. 9 dB over the whole wire length
-
Cross section: max. 0.34 mm2 , corresponding to AWG 22
-
Cable type: twisted in pairs, 1 x 2, or 2 x 2, or 1 x 4 wires
-
Screening: Copper-braided screen or braided screen and foil screen
Use of the same cable type throughout the entire network is recommended to avoid impedance mismatch.
The numbers on the following diagram indicate the maximum number of stations in each segment. They are
not the station addresses, as each station in the network must have a unique address.

EMC Precautions

The following EMC precautions are recommended to achieve interference-free operation of the PROFIBUS
network. Additional EMC information is available in the FC 300 series Quick Guide and Source Book. Please
also consult the PROFIBUS master manual for further installation guidelines.
NB!:
Ensure compliance with relevant national and local regulations, for example in protective earth
connection.
Connection of the Cable Screen
The screen of the PROFIBUS cable must always be connected to ground at both ends, meaning the screen
must be connected to ground in all stations connected to the PROFIBUS network. It is very important to
have a low impedance ground connection of the screen, also at high frequencies. This can be obtained by
connecting the surface of the screen to ground, for example by means of a cable clamp or a conductive cable
gland. The FC 300 Series has various clamps and brackets to enable a proper ground connection of the
PROFIBUS cable screen. The screen connection is shown in the section Connecting the Bus Line.
14
How to Install
MG.33.C2.02 - VLT is a registered Danfoss trademark