BECKHOFF BK7500 - Manual (Page 12)

Basic information
12 BK7500
Insulation test
PE power contacts 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 couplers 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.
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 coupler 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.