25
User Manual
MN013016EN
Effective July 2022
Magnum PXR and Power Defense SB low
voltage power circuit breakers user manual
EATON
www.eaton.com
Current sensors
The internal Current Sensors are permanently installed in the lower
rear of the circuit breaker . They consist of two coils; as current
begins to flow through the circuit breaker, an iron core coil generates
the energy which powers the trip unit . At the same time, an air
core coil provides signals which are processed to determine the
magnitude of current the breaker is carrying . Auxiliary control power
is not required for current protection functions .
Figure 32. Narrow frame current sensors shown with cover plate
removed
Trip actuator
The trip actuator is a small cylindrically shaped electromagnetic
device that acts mechanically to trip the circuit breaker
(
) . In general, it is composed of a permanent magnet,
a spring-loaded rod to produce the mechanical tripping, and a lever
for resetting the actuator after tripping occurs . The electronic trip
unit provides a pulse that counteracts the effect of the permanent
magnet, allowing the spring-loaded rod to act mechanically .
The device is reset when the circuit breaker opens .
Mechanical trip flag
A red, pop-out mechanical trip indicator is an optional feature . It is
located above the trip unit on the breaker’s front faceplate
(
) . It operates by releasing and popping out any time the
circuit breaker trips due to an overcurrent condition .
An optional overcurrent trip switch (OTS) that operates off the
position of the mechanical trip indicator is also available . The switch
is reset when the trip indicator is reset .
The pop-out mechanical trip indicator is available in two versions:
Interlocking trip indicator
—When activated via a tripping event,
the interlocked version of the trip indicator acts to provide local
visual indication that the breaker has tripped, change the OTS
contact position, and interlock the breaker such that the breaker
cannot be reclosed until the mechanical trip indicator is reset .
Non-interlocking trip indicator
—This version acts only to provide
visual local indication of a tripping event and change the OTS
contact position .
When using an interlocking trip indicator, a remote trip reset option
is available to electrically reset the trip indicator by applying the proper
rated control voltage . The remote trip reset feature is very useful in
applications where direct access to the circuit breaker is limited, for
example a wind turbine . The remote trip reset will act to reset the
trip indicator and OTS but will not reset the trip unit status LEDs;
those can be reset via communications (if included) .
The PXR trip unit shows the cause of trip via LEDs on the face of
the trip unit . These indicators should be cleared by pushing the reset
button after the cause of the fault has been diagnosed . This will
preserve the battery and eliminate confusion when the breaker is
put back in service .
Making current release
All Magnum PXR and PD-SB circuit breaker trip units have a making
current release function . This safety feature prevents the circuit
breaker from being closed and latched on a faulted circuit . The
non-adjustable release is preset at a peak instantaneous current
of 22 .5 x I
n
; this corresponds to an rms current of 11 x I
n
with
maximum asymmetry .
The making current release is enabled only for the first two cycles
following a circuit breaker closing operation . The making current
release will trip the circuit breaker instantaneously, release the
mechanical (pop-out) indicator, and flash the instantaneous LED
trip indicator, if so equipped .
Voltage taps
On circuit breakers with the PXR 25 trip unit, voltage taps will be
pre-installed for monitoring the three phase voltages . One set (red
wires) connects to the line (upper) terminals and the other set
(black wires) connects to the load (lower) terminals (black tubing
does not extend to the connection at the terminals) . Either is then
connected to the Voltage Module which converts line voltage for
input to the trip unit .
The voltage tap connectors at the front of the breaker
are
equipped with a protective insulating cap . Be sure to leave the cap in
place over the unused connectors .
Breakers are able to be converted from upper terminal voltage
monitoring to lower terminal voltage monitoring by switching
the connections with the voltage divider board connector . If the
connection is switched, replace the cap over the unused connector
and contact Eaton for a Lower Terminal Voltage Metering Label .
Figure 33. Line and load-side voltage taps for circuit breakers
with PXR 25 trip unit
Line-Side
(Upper)
Voltage Tap
Load-Side
(Lower)
Voltage Tap
