BECKHOFF BC3150 - Manual (Page 19)

Safety Instructions
Fieldbus Components 17
Wiring
Potential Groups, Insulation Testing and PE
Potential groups
The Beckhoff Bus Terminals stations usually have three different potential groups:
•
The fieldbus interface is electrically isolated (except for individual Low Cost couplers) and forms the first po-
tential group
•
Bus Coupler / Bus Terminal Controller logic, K-Bus and terminal logic form a second galvanically separated
potential group
•
The inputs and outputs are supplied via the power contacts and form further potential groups.
Groups of I/O terminals can be consolidated to further potential groups via potential supply terminals or separation
terminals.
Insulation 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 K-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.