Siemens SINUMERIK ONE NCU 1760, Руководство по эксплуатации оборудования

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7.9.3 Connection components in PROFIBUS
Connection components
Individual nodes are connected by means of bus connectors and PROFIBUS cables.
Remember to provide a bus connector with a programming port at either end of the subnet. This
will give you the option of expanding the subnet if required, for example, for a programming
device.
Use RS 485 repeaters to connect segments or extend cable lengths.
Segments
A segment is a bus line between two terminating resistors. A segment may contain up to 32
nodes. In addition, a segment is limited by the permissible cable length, which varies according
to the transmission rate.
Terminating resistor
A cable must be terminated with its own surge impedance to prevent line disturbances caused
by reflections. Activate the terminating resistor at the first and last node on a subnet or segment.
The NCU must be either the first or the last node on the subnet.
Make sure that the stations to which the terminating resistor is connected are always supplied
with voltage during power-up and operation.
7.9.4 Rules for the laying of PROFIBUS cables
Laying of bus cables
During laying of the PROFIBUS cable, you must avoid:
● twisting
● stretching and
● squeezing
Supplementary conditions
During laying of the indoor bus cable, you must also consider the following supplementary
conditions (d
O
= outer diameter of the cable):
Table 7-17 Supplementary conditions for the laying of PROFIBUS cables
Characteristics Supplementary conditions
Bending radius for a single bend 80 mm (10xd
O
)
Bending radius (multiple times) 160 mm (20xd
O
)
Connecting
7.9 PROFIBUS DP
NCU 1760
72
Equipment Manual, 02/2020, A5E45627861B AB