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4 Communication functionality
PXR tRiP units foR PoweR Defense molDeD case ciRcuit bReakeRs
MN012007EN June 2018 www.eaton.com
3.9 Operating temperature
All models of trip units are designed for commercial/industrial circuit breaker environments.
The frames are rated for load and temperature per individual circuit breaker. As an additional
protection, if temperatures in the PXR trip-unit exceed 105 °C (220 °F), a factory-set over-
temperature protection feature will trip the circuit breaker to protect the internal electronic
components.
4 Communication functionality
The PXR family of trip units offers wide support for communications. A USB port is present
on all PXR family trip units. All PXR 20, 20D and 25 support external communication adapter
modules (CAM) while certain models have built-in Modbus-RTU.
4.1 Integrated Modbus - remote terminal unit (RTU)
A Modbus communication port is integrated into the PXR trip unit for certain styles. Breaker
status (closed/tripped/open), set points and operating information are all available via
Modbus. The trip unit responds to messages from the master using the remote terminal
unit (RTU) protocol. Modbus port configuration can be viewed and set using the user
interface (UI) or using Power Xpert Protection Manager software. The trip unit uses Modbus
function codes 02, 03, 04, 06, 08, and 16 and supports up to 122 registers (244 bytes) in a
single Modbus transaction.
The detailed Modbus register map is shown in Section 10: Modbus communication port
register map.
4.2 USB port
The PXR includes a micro-B form USB port on the front of the trip unit. This USB connection
is used in conjunction with your PC running the PXPM software to configure, control, and
test the trip unit. The USB host-side also supplies power to the electronics for configuration
when the circuit breaker is not carrying current or when no auxiliary power is applied and for
trip unit testing (both trip and no-trip). A commercial USB battery supply may also be used.
The USB port is covered by the clear, lockable cover to prevent unauthorized modification to
settings. Controlling physical access to the USB port is a key element in your comprehen-
sive cyber security plan.
4.3 External communications adapter modules (CAMs)
The PXR 20, 20D and 25 trip units are equipped to handle a flexible and modular system of
communication adapter modules (CAMs). These modules provide communication from the
trip unit to a field bus network. These modules mount on a DIN rail and wired into the trip
unit.
