ABB AC 800M User Manual page 27

Section 2 Transmission Technology
Project-specific requirements and limitations such as underground wiring, UV
resistance, being free of halogen, etc. should be considered when selecting the
cable. Cables may be used with deviate mechanically or electrically from the type A
cable, but the surge impedance must be retained.
Note that cable for laying underground is not suitable for connecting to
PROFIBUS connectors because of the typically 10 mm diameter of the coating.
They can therefore only be connected to screw terminals of PROFIBUS devices.
Depending on the ambient EMC conditions, EN 50170 also allows for laying of
unshielded cable. However, the following reasons argue in favour of always using
shielded cable:
The only interference-free space is inside the switch cubicle, at best. As soon as a
relay is located within the switch cubicle, this is no longer the case.
Unshielded cable requires additional protective measures at the bus inputs to
protect against voltage overload.
From the line parameters specified above result the following bus segment lengths
Transmission rate in kbit/s
Range in m/segment
In a PROFIBUS DP installation, it must be chosen a data transfer rate which is
supported by all devices connected to the bus. The chosen data transfer rate then
determines the maximum segment lengths as shown above.
If other transmission rate shall be used which is not listed in the table above, an
approximation can determine the permissible length through linear interpolation of
two adjacent transmission rates from the table.
3BDS009029R5001 B
Table 2. Basic data for a PROFIBUS DP reference cable
Wire diameter
Wire cross-section
Table 3. Dependencies of bus length and transmission rate
9.6
1200
RS485 cable type and speed
> 0.64 mm
2
> 0.34 mm
19.2 93.75 187.5
1200 1200 1000
500 1500 12000
400 200 100
:
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