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MaGnuM PRoDuct GuiDe
CA013002EN—April 2017 www.eaton.com
50
Magnum trip units and communication devices
Other communication related devices
Most Digitrip trip units can
be simply integrated with
additional features provided
by other closely associated
communication related
devices and/or external
accessories . A Digitrip tripping
system is extraordinarily
versatile, capable of providing
a complete set of functions
for protection, measurement,
signaling, data storage and
control of the circuit breaker .
•
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 . This device is located
just above the trip unit on
the breaker’s front faceplate .
In the event the trip unit
trips the breaker on an
overcurrent condition, the
red trip flag releases and
pops out to give local visual
indication . This trip indication
is in addition to any LED
trip indication next to the
protection feature .
The red flag can be reset by
manually pushing it back in .
The breaker can be reclosed,
even if the flag is not reset .
An optional Overcurrent Trip
Switch (OTS) is available
should an electrical
lockout be required on an
overcurrent trip condition .
•
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
non-adjustable, preset to
trip the breaker when the
peak instantaneous current
exceeds 25 x In (In is
established by the breaker’s
current sensors and rating
plug) . 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 if the breaker
is so equipped .
•
Bell alarm/Overcurrent
Trip Switch (OTS):
The Bell Alarm/Overcurrent
Trip Switch (OTS) is an
overcurrent indication
feature that can be supplied
as an option on Magnum
breakers with integral trip
units . The OTS Switch
includes 2 Form C contacts
that are wired to the breaker
secondary terminals . These
contacts are available for
external wiring to provide
remote trip indication or
for electrical lock-out of a
breaker .
If the trip unit trips the
breaker on an overcurrent
condition:
•
Red mechanical trip flag
indicator pops out
•
OTS contacts change
state
The OTS Switch is reset by
manually pushing in the red
trip flag . When the trip flag
is reset, the OTS switch
contacts return to their
normal state .
•
High instantaneous trip:
Magnum breakers that
are rated 100kA and
manufactured in the
standard frame with 800 to
3200 ampere continuous
current ratings (MDSC08
to MDSC32) are equipped
with a high instantaneous
trip . This instantaneous trip
system consists of small
air core sensors (one per
phase) which produce a
signal and transmit it back
to the trip unit . When the
fault current approaches
the 85kA 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 available fault
current while maintaining
selectivity up to 85kA .
•
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
overtemperature 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 circuit 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 circuit .
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 moving a jumper
located inside the cavity
behind the test port cover .
to the inactive position . The
LTM can be reactivated by
returning the jumper to the
active position .
•
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 temperature of
the trip unit exceeds 85°C .
This is the approximate
manufacturer’s published
maximum temperature
rating for the trip unit
electronic components .
An 85°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
Time Delay LED of the trip
unit will flash if the breaker
is so equipped .
