PROFIBUS MODULE (CB15/CB155)
English
Operating Instructions
9
2.3 EMC Measures
The following measures are required for interference-free operation of the PROFIBUS-DP. Additional information
on EMC precautions can be found in the ‘ET 200 Distributed I/O System’ manual.
2.3.1 Shielding
The conductors of the bus cables must be twisted together, shielded and installed separately from the power
cables with a minimum clearance of 20 cm. The shield for the bus cable should be connected to protective earth at
both ends.
For the CB15, this is achieved using the P-clip provided with the module as shown in the enclosed instruction
sheet.
For the CB155, if the specified cables are used, no further action is necessary.
Bus and power cable crossings should be installed at an angle of 90o.
2.3.2 Equipotential Bonding
If the cable shields are earthed at different sections of the system then equipotential bonding cables can be used to
reduce current flow in the screen between the inverters and the PROFIBUS-DP master.
The following equipotential cables are recommended:
16 mm2 Cu for equipotential bonding conductors up to 200 m in length
25 mm2 Cu for equipotential bonding conductors over 200 m in length
Use a large contact surface connection between the equipotential bonding conductors and the protective ground
conductor.
2.3.3 Cable Installation
Observe the following rules when installing cables:
-
Bus cables (signal cables) may not be installed directly adjacent to power cables.
-
Signal cables (and equipotential bonding cables) should be connected across the shortest possible path.
-
Power cables and signal cables must be installed in separate cable runs.
-
Shields should have large contact surface connections.
2.4 PROFIBUS-DP Bus Termination
For interference-free operation of PROFIBUS-DP, the bus cable must be terminated at both ends with bus
terminating resistors. The bus cable from the first PROFIBUS-DP station to the last PROFIBUS-DP station should
be treated as a single bus cable, so that the PROFIBUS-DP should be terminated twice.
The bus terminators must be connected to the first station (e.g. the master) and the last station (slave).
For the CB15, this is achieved by moving the switch mounted on the D-type of the PROFIBUS-DP connector to the
ON position.
For the CB155 this is achieved by fitting the dedicated terminating connector to the free position on the T connector
at the end of the link.
Note
(1) Ensure that you only connect the bus terminator to the first network station and the last network
station.
