BECKHOFF BC3100 - Manual (Page 11)

Basic information
BC3100 11
Insulation test
PE power contacts You open a spring terminal by applying a slight pressure with a screwdriver
or other pointed tool in the opening above the terminal and you can then
insert the wire into the terminal without any obstruction. When you release
the pressure the terminal will automatically close and hold the wire
securely and permanently.
The connection between bus terminal controller and bus terminals is
automatically effected by latching the components together. The K bus is
responsible for passing data and power to the electronic components of the
bus terminals. In the case of digital bus terminals, the field logic receives
power via the power contacts. Latching the components together has the
effect that the series of power contacts constitutes a continuous power
track. Please refer to the circuit diagrams of the bus terminals: some bus
terminals do not loop these power contacts through, or not completely (e.g.
analog bus terminals or 4-channel digital bus terminals). Each power input
terminal interrupts the series of power contacts and constitutes the
beginning of a new track. The bus terminal controller can also be used to
supply power to the power contacts.
The power contact labeled "PE“ can be used as protective earth or ground.
This contact stands proud for safety reasons and can carry short-circuit
currents of up to 125A. Note that in the interests of electromagnetic
compatibility the PE contacts are capacitively connected to the supporting
track. This may lead to spurious results and even damage to the terminal
when you test the insulation (e.g. insulation test for breakdown using a
230V mains supply to the PE line). You should therefore disconnect the PE
line on the bus coupler while you carry out insulation tests. You can
disconnect other power supply points for the duration of the test by drawing
the power supply terminals out from the remaining row of terminals by at
least 10mm. If you do this, there will be no need to disconnect the PE
connections.
The protective earth power contact ("PE“) may not be used for any other
connections.