Operating instructions

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.
2.1.2. EMC Precautions
The following EMC precautions are recommended to achieve interference-free operation of the
PROFIBUS network. Additional EMC information is available in the relevant FC 100, 200 or 300
series Operating Instructions (MG.11.AX.YY, MG.20.NX.YY or MG.33.AX.YY) and Design Guides
(MG.11.BX.YY, MG.20.MX.YY or MG.33.BX.YY). Please also consult the PROFIBUS master manual
for further installation guidelines.
NB!
Ensure compliance with relevant national and local regulations, for example in pro-
tective earth connection.
2.1.3. 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 frequency converter has various clamps and
brackets to enable a proper ground connection of the PROFIBUS cable screen. The screen con-
nection is shown in the section
Connecting the Bus Line .
2. How to Install VLT
®
Profibus
14 MG.33.C4.02 - VLT
®
is a registered Danfoss trademark
2