Beckhoff EL2904 - Page 27

Operation
EL2904 27Version: 3.2.2
NOTICE
Observe the E-bus current
Observe the maximum current that your Bus Coupler can supply to the E-bus! Use the EL9410 Power
Supply Terminal if the current consumption of your terminals exceeds the maximum current that your Bus
Coupler can feed to the E-bus supply.
Power contacts
The power contacts deal with the supply for the field electronics and thus represent a supply rail within the
Bus Terminal block. The power contacts are supplied via terminals on the Bus Coupler.
Note the connection of the power contacts
During the design of a Bus Terminal block, the pin assignment of the individual Bus Terminals must
be taken account of, since some types (e.g. analog Bus Terminals or digital 4-channel Bus
Terminals) do not or not fully loop through the power contacts.
Potential supply terminals (EL91xx, EL92xx) interrupt the power contacts and thus represent the
start of a new supply rail.
PE power contact
The power contact labelled 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.
Fig.7: PE power contact
CAUTION
Insulation tests
Note that, for reasons of electromagnetic compatibility, the PE contacts are capacitatively coupled to the
mounting rail. This may lead to incorrect results during insulation testing or to damage on the terminal (e.g.
disruptive discharge to the PE line during insulation testing of a consumer with a rated voltage of 230V).
For insulation testing, disconnect the PE supply line at the Bus Coupler or the Potential Supply Terminal! In
order to decouple further feed points for testing, these Power Feed Terminals can be released and pulled at
least 10mm from the group of terminals.
DANGER
Serious risk of injury!
The PE power contact must not be used for other potentials!