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Power Circuit Breokers,
GEK-731O
UNDERVOLTAGE
DEVICE
The undervoltage
device
trips the
breaker
when
its coil is de-energized.
The leads
of the coil
are
connected
directly to
secondary disconnects
or to
a
terminaL
board.
Under
normal conditions, the coil
remains energized
and
the
breaker may
be closed.
"Drop
out" of the
armature,
with
resultant
breaker tripping, occurs
when
the voltage
is re-
duced
to
Iess
than
60
percent of the rated voltage.
An open
armature
willrenderthe
breaker
incapable
of
closing.
The armature "picks up"
ald
allows
closing, if
the voltage
is
85
percent
or
more of its
nominal value.
If
the breaker
is
disconnected,
and
for
some
reason
the breaker
is
to be operated
manually,
the
undervoltage device
may be
tied or
wired
down
so
that
it
wiII not
cause
tripping.
MAIN SHAFT
(BREAKER
CLOSED)
Fig.
9.
(0134C2181) Holding
link
on
electric
lockout deuice
STAT]C
TIIYIE-DEIAY
UN
DERVOTTAGE
In
addition
to the
instantaneous undervoltage
tripping
device mounted
on the breaker, the static
time-delay
undervoltage includes
a
separately
mounted
time-delay
unit.
Its
diagram
is
shown
in
Fig. 21.
If
the.aic control
voltage
is
anyvoltage
other than 208/240V ac,
a
control
power trans-
former
(also remotely
mounted
with
respect
to
the
breaker) must be
used. This must
have
a minimum
rating of
100
volt-amperes.
When
installed, the voltage to be monitored is
connected
across
terminal.s
No.
1
and
No.
2 of
the
static
delay
box.
The
coil of
the tripping unit is
connected
across
terminaLs
No.
4
and
No.
5
of the
static box through the secondary disconnects of
the
breaker. The
secondary disconnects
to
be
used
will
be shown
on
the
breaker wiring diagram.
No more than
one
undervoltage
tripping
device
should
be
used in conjunction
with
one
static time-
delay unit.
The
static time-delay
undervoltage
can
also
be
furnishedwitha thermotector controlunit, as
shown
on
wiring diagram,
Fig.
22.
Overheating
of motor
windings causes the
thermotector,
imbedded
in
the
motor
windings,
to
open. This de-energizes
the
undervoltage
device on the breaker
and
drops
the
motor
load.
ETECTRIC
LOCKOUT
DEVICE
The electric lockout
device
utilizes
an under-
voltage device
to
keep
the breaker
from
resetting
its
mechanism
i-f
the
breaker
is
open
and
the under-
voltage device
coil is
not energized.
The
breaker
thus cannot be closed unless
voltage
is
on
the
coil.
Once
the
breaker is closed, Ioss of voltage
wiII
not
trip
the
breaker because, in
the
closed position,
a
mechanical
link
is
used
to
hold down the
armature
of
the
device.
See
Fig.
9.
This
arrangement
pro-
vides
a
means
of
electrically
interlocking
two
breakers
so
that they cannot be
closed
at
the
same
time.
Each undervoltage
coil
may be
wired
in
series
with
a '8"
auxiliary switch
contact on
the
other breaker
for cross-interlock
purposes.
On
each
breaker having an electric lockout,
an
arrangement
is
made
which
will
allow
breaker
closing
with the
coil
de-energi-zetl.
This
is
pro-
vided
to
aLlorr
'?start-up" on "dead"
systems. Fig-
ure
10
shows
this device.
The push
slide
shown
is
located in
the
opening
in
the lower part of
the
es-
cutcheon. The breaker doormust be
opened
to
gain
access
to it.
HOLD.IN
13
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