SEW-Eurodrive INTERBUS UFI11A Manual page 16

4
Installation and Operation with a PC
24 V connection
Shielding and
routing of the bus
cables
16
• Switch on the system bus terminating resistor (S12 = ON) of the node end of the sys-
tem bus. Switch off the terminating resistor on the other units (S12 = OFF). The
UFI11A fieldbus interface must always be the first or last node on the system bus. It
has an integrated terminating resistor.
• There must not be any potential difference between the units connected to the SBus.
Take suitable measures such as connecting each unit's ground lug to a central
grounding point in the cabinet to avoid potential differences.
• Point-to-point cabling is not permitted.
An external 24 VDC voltage supply must be connected to terminals X1:4 and X1:5.
The voltage range for the 24 VDC voltage supply is 18 – 30 V. The current consumption
of the UFI11A fieldbus interface is 300 mA.
The INTERBUS interface supports RS-485 transmission technology and requires the
cable type specified as the physical medium for INTERBUS. This cable must be a shiel-
ded, twisted-pair cable with 3 x 2 cores.
Having the bus cable correctly shielded eliminates parasitic interference which can oc-
cur in an industrial environment. The following measures ensure the best possible shiel-
ding:
• Finter-tighten the retaining screws of plugs, modules and equipotential bonding con-
ductors.
• Use only connectors with a metal housing or a metallized housing.
• Maximize the contact area between the shield and the connector housing.
• Shield the bus cable on both ends.
• Do not route the signal and bus cables in parallel with the power cables (motor
leads); use separate cable ducts if possible.
• Only use grounded-metal cable trays in industrial environments.
• Join the signal cables and the associated equipotential bonding together at closely
spaced intervals by the shortest route.
• Avoid using plug connectors to extend bus cables.
• Route the bus cables closely adjacent to available grounding surfaces.
In the event of fluctuations in the ground potential, a compensating current may flow
along the shield which is connected at both ends and to the ground potential (PE). In this
case, make adequate provision for equipotential bonding in accordance with the rele-
vant VDE regulations.
Manual – Fieldbus Interface INTERBUS UFI11A