Eaton PXR10 Manual page 46

7 Auxiliary wiring terminals
7.1 Interface module
42
Replacing the interface module
The interface module, which is pre-installed in all PXR25 trip units, rarely
needs to be replaced. For all PXR20 devices, the interface module is an
optional accessory that is required, among other things, for connecting a
communication module. On PXR20 devices it can also be retrofitted.
Voltage tap for the neutral conductor
The VN connection is located on the side of the interface module (only on the
3-pole NZM4 circuit breakers with energy metering (PXR25)). On the 3-pole
NZM4 circuit breakers with energy metering (PXR25), the VN module, which
occupies slot HIA 4.1, is already pre-installed. The voltage tap for the neutral
connector is connected at the VN module. This is necessary to ensure
measurements with maximum accuracy. Otherwise the electronic trip unit
will not be "familiar" with the star point of the system. The VN module
contains a chain of resistors that is calibrated to the overall system.
When replacing the interface module of a 3-pole NZM4 circuit breaker with
energy metering (PXR25), do not remove or replace the VN module. It may
be removed briefly to replace an old interface module and must then be
reinstalled together with the new interface module, ￫ section 3.6, "Voltage
tap of the neutral conductor on the PXR25", page 23.
The PXR20 trip units do not have a voltage tap for the neutral conductor,
as they do not measure the voltage.
Figure 11: Removing the interface module
PXR Electronic trip unit 01/21 MN012005EN www.eaton.com