16 Unidrive M SI-PROFIBUS User Guide
Issue Number: 3
4.2 PROFIBUS-DP connectors
There are numerous manufacturers of PROFIBUS-DP connectors. Always ensure that
any connectors used on the network are fully approved for use with PROFIBUS-DP
networks. Some of the connector types available include built in termination that allows
the network to be isolated, this can be very useful when fault finding. For data rates
above 1.5 Mbs connectors installed with integrated inductors should be used.
4.3 PROFIBUS-DP cable
PROFIBUS-DP networks can run at high data rates and require cable specifically
designed to carry high frequency signals. Low quality cable will attenuate the signals,
and may render the signal unreadable for the other nodes on the network. Cable
specifications and a list of approved manufacturers of cable for use on PROFIBUS-DP
networks are available on the PROFIBUS Nutzerorganization (PNO) website at
www.profibus.com.
4.4 Cable shielding
Correct shielding of the PROFIBUS-DP cable is required for reliable operation at high
data rates, this can be achieved by exposing the cable shield of each PROFIBUS-DP
cable and ensuring that they are clamped to the drive grounding metalwork as close as
possible to the drive termination, contact your supplier or local Control Techniques Drive
Centre for more information.
4.5 General grounding considerations
It is essential that good grounding is provided not only for network stability but more
importantly electrical safety. In all instances electrical regulations should be adhered to.
As a guide the network cable should be grounded at least once per cabinet, ideally on
each drive.
4.6 Network termination
It is very important in high-speed communications networks that the network
communications cable is installed with the specified termination resistor network at each
end of each segment. This prevents signals from being reflected back down the cable
and causing interference.
Most ranges of connectors provide specific parts that incorporate the termination
network. Such connectors derive the power from the host device and if the host device
is switched off the termination will be lost. To avoid this situation a separate termination
device is available that is powered independently of the network devices. For more
information go to www.profibus.com.
Control Techniques can only guarantee correct and reliable operation of the SI-
PROFIBUS if all other equipment on the PROFIBUS-DP network (including the network
cable) has been approved by the PNO and is correctly installed.
Unless there are specific reasons for not grounding the network it is recommended that
all drive network connections are correctly grounded. Failure to do so may reduce the
noise immunity of the system. If there are specific issues with grounding, alternative
methods of connection should be considered such as the use of fibre optic cable.
Failure to terminate a network correctly can seriously affect the operation of the network.
If the correct termination networks are not installed, the noise immunity of the network is
greatly reduced. Each network segment must be correctly terminated.
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