NORD Drivesystems BU0020 - Manual (Page 44)

PROFIBUS DP – Supplementary manual options for NORD - Frequency Inverters
44 BU 0020 GB-2612
4. Bus Configuration
A bus segment consists of a maximum of 32 participants. Several segments can be connected
together by means of repeaters. In this way, up to 126 participants can participate in reference data
traffic. It should be noted that the reaction time increases as the number of participants increases.
The data transfer physics of the serial bus system by means of twisted two-
wire cable (with connected shielding) is defined in the specification of the
interference-proof RS485 interface.
Optic fibre cables should be used for applications with a high potential for
electromagnetic interference and long distances.
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4.1 Laying the bus cables
In an industrial environment the correct installation of the bus system is particularly important in order
to reduce potential interference. The following points are designed to help prevent interference and
problems right from the start.
The installation guidelines are not complete and applicable safety and
accident prevention guidelines must be complied with.
Installation information and recommendations for laying are given in
Section 4.4.
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4.2 Cable material
The frequency inverter is usually connected to the PROFIBUS system by a twisted, shielded two-wire
cable. In EN 50 170, this bus cable is specified as cable type A. The guaranteed transfer speeds or
transfer distances can only be achieved without errors if the specific cable parameters are complied
with.
With these cable types, the following lengths of a bus segment result:
Transfer rate
Baud rate [kBit/s]
9.6 19.2 45.45 93.75 187.5 500 1500 3000 6000 12000
Cable length [m]
Cable type A
1200 1200 1200 1200 1000 400 200 100 100 100
Table 6: Transfer speeds versus cable length
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