ABB AC500 PLC Hardware Manual page 1286

System Assembly, Construction and Connection
AC500 (Standard) > Connection and Wiring
Multiple switch-gear cabinets: If potential differences can occur between the switch-gear cabi-
nets, the capacitive earthing method is chosen in order to avoid circulating currents on the cable
shields.
Fig. 238: Earthing concept with several switch-gear cabinets: direct earthing of cable shields
when cables enter the first switch-gear cabinet (containing the master), and capacitive earthing
at the modules
Everywhere is valid: The total length of the earthing connections between the shield of the Ter-
minal Base and the earthing bar must be as short as possible (max. 25 cm). The conductor
cross section must be at least 2.5 mm².
2.6.4.9 CANopen Field Bus
Types of Bus For CANopen, only bus cables with characteristics as recommended in ISO 11898 are to be
Cables used. The requirements for the bus cables depend on the length of the bus segment. Regarding
this, the following recommendations are given by ISO 11898:
1286
Cabinet 1
COM1
PE
1
2
3
4
120
CS31 bus master
Ohms
e.g. PM581
Cabinet earthing
Cabinet 2
120
Ohms
CS31-
Slave
PE
Cabinet earthing
VDE 0160 requires, that the shield must be earthed directly at least once per
system.
3ADR010121, 13, en_US
CS31 system bus
CS31
slave
PE
Earthing bar of cabinet 1
capacitive earthing with 0.1 uF
X-type capacitor directly on the
cabinet's steel plate
CS31-
Slave
PE
direct
earthing
with clip
on cabinet
steel plate
CS31-Systembus
Earthing bar
of cabinet 2
2019/04/17