I/O Terminal /
MOUNTING AND WIRING
16
3.3.2 Insulating
Testing
The connection between the Bus Coupler / Bus Terminal Controller and the Bus Terminals is
automatically realized by pushing the components together. The transfer of the data and the
supply voltage for the intelligent electronics in the Bus Terminals is performed by the
Standard-Bus. The supply of the field electronics is performed through the power contacts.
Plugging together the power contacts creates a supply rail. Since some Bus Terminals (e.g.
analog Bus Terminals or 4-channel digital Bus Terminals) are not looped through these
power contacts (or not completely) the Bus Terminal contact assignments must be
considered.
The potential feed terminals interrupt the power contacts, and represent the start of a new
supply rail. The Bus Coupler / Bus Terminal Controller can also be made use of to feed the
power contacts.
3.3.3 PE Power Contacts
The power contact labeled PE can be used as a protective earth. For safety reasons this
contact mates first when plugging together, and can ground short-circuit currents of up to 125
A.
It should be noted that, for reasons of electromagnetic compatibility, the PE contacts are
capacitively coupled to the mounting rail. This can both lead to misleading results and to
damaging the terminal during insulation testing (e.g. breakdown of the insulation from a 230
V power consuming device to the PE conductor). The PE conductor to the Bus Coupler / Bus
Terminal Controller must be disconnected for the insulation testing. In order to uncouple
further feed locations for the purposes of testing, the feed terminals can be pulled at least 10
mm out from the connected group of other terminals. In that case, the PE conductors do not
have to be disconnected.
The PE power contact must not be used for other potentials.
