36
PXR trip unit and communication modules
MAGNUM PXR PRODUCT GUIDE
PA013006EN September 2022 www.eaton.com
3
Mechanical trip flag pop-out indicator
The mechanical trip flag pop-out indicator is an overcurrent
indication feature that can be supplied as an option on
Magnum breakers with integral trip units. Refer to
Section
4:
Magnum PXR accessories - Mechanical trip flag pop-out
indicator for more details.
Bell alarm/overcurrent trip switch (OTS)
The Bell Alarm/Overcurrent Trip Switch (OTS) is an overcur-
rent indication feature that can be supplied as an option on
Magnum breakers with integral trip units. Refer to
Section
4:
Magnum PXR accessories - Mechanical trip flag pop-out
indicator for more details.
Making current release
The Making Current Release (MCR) is a standard safety
feature provided on all Magnum breakers equipped with
integral trip units. The MCR provides an instantaneous trip
when closing on a fault current, which exceeds a specified
magnitude. The MCR is not adjustable, preset to trip the
breaker when the peak instantaneous current exceeds
22.5 x I
n
. The I
n
is established by the breaker’s current
rating and is marked by the plastic plug below the trip unit
The MCR is enabled for only the first two cycles following
the breaker closing operation. When the MCR trips the
breaker, the red trip flag of the mechanical indicator will
pop out and the red Instantaneous LED, labeled (Inst.), of
the trip unit will flash.
Fixed internal instantaneous override trip
Magnum breakers that are rated 100 kA and manufactured
in the standard frame with 800 to 3200 ampere continu-
ous current ratings (MPSC08 to MPSC32) and narrow
frame with 800 to 2000 ampere continuous current ratings
(MPNC08 to MPNC20) are equipped with a high internal
instantaneous trip. When the fault current approaches the
withstand rating of the circuit breaker, the trip unit trips
the breaker instantaneously. This allows the breaker to be
applied on a power distribution system with a 100kA avail-
able fault current while maintaining selectivity.
Long time memory (LTM)
Long Time Memory (thermal memory) is a standard
feature on Magnum breakers supplied with integral trip
units. The thermal memory function provides overtem-
perature protection on load circuits against the effects of
repeated overload conditions.
If a breaker is closed soon after an overload trip and the
current again exceeds the Long Delay Setting, the LTM
reduces the time to trip. This allows for the fact that the
load or cable temperature is higher than normal due to the
previous overload condition. If the breaker continues to
be closed into repeated overload conditions, the breaker
will trip in successively shorter times to allow for the
cooling of the load. When the overload condition returns
to normal, the LTM function begins to slowly reset. It will
fully reset back to the normal Long Delay Time setting
after about 10 minutes, provided that another overload is
not experienced.
In some applications, for example fire pumps, electric
welders or during primary injection current testing, it may
be desirable to defeat the LTM. This can be accomplished
at the trip unit by programming the LTM function through
the display or through PXPM to OFF / disable.
Over temperature trip
Magnum breakers equipped with integral trip units are
provided with a standard over temperature trip function. It
is designed to trip the breaker when the internal tempera-
ture of the trip unit exceeds 95°C.This is the approximate
maximum temperature rating for the trip unit electronic
components. A 95°C temperature inside the trip unit
indicates that there are much higher temperatures and
potentially significant heating problems elsewhere in the
circuit breaker enclosure.
When the over temperature function trips the breaker, the
red trip flag of the mechanical indicator will pop-out and
the red LONG LED on the trip unit will flash.