Maintenance - GE AKR-75 Series Instructions - Installation And Operation

GEt-861518
TRIPPING
In
the closed position,
the breaker's movable contacts are
held in
by a
toggle linkage. The breaker
is
tripped open
by
displacing a mechanism latch which allows this toggle
link-
age to collapse. The trip latch is rigidly fastened
to a
horizon-
tal trip shaft running from
left
to
right through the breaker.
In
turn,
the
trip shaft carries paddles actuated
by
the manual trip
button
and the various other trip
devices
-
overcurrent,
reverse
current,
shunt trip, undervoltage, open fuse lockout.
Viewing the
breaker
from the right,
rotating the
trip
shaft
counterclockwise
trips the breaker; clockwise movement re-
sets
the
mechanism
latch.
In
addition
to
tripping the
breaker, some devices hold the
breaker trip
free,
i.e., prevent the contacts from closing even
though
a
closing
impulse
is
applied to the mechanism.
Such
devices
are
the undervoltage,
bell alarm and lockout,
electric
lockout, open fuse lockout, and
the key
operated
locks.
These
devices
and the
drawout mechanism interlocks
must
be in the reset position before the breaker can be
closed.
Breakers employed in
conjunction
with fuse
rollout ele-
ments should be equipped with an open fuse lockout device
(OFLO). This OFLO
is a special trip device having
three
(3)
shunt
trip elements (one per phase), the coil of each
being
connected across its corresponding fuse in the fuse
rollout
unit.
Connections
are made via
the
C
secondary disconnect
block on
the breaker
thru
the
B
secondarv disconnect
block
on
the fuse rollout
unit.
The arc voltage generated by a
blown
fuse
activates its
OFLO shunt
trip
coil, thereby tripping the breaker and pre-
venting single phase
power from
being supplied to
the
load.
An indicator
on
the OFLO device signals which fuse
is
blown.
The
breaker cannot be closed until
the
blown
fuse
is
ac-
knowledged by resetting the
OFLO, and
presumably
replac-
ino
the
blown fuse.
MAINTENANCE
INSPECTION
Periodic inspection
of the
circuit breaker
is recommended
at least once a year. More frequent inspections are
recom-
mended
where severe load
conditions, dust,
moisture or
other unfavorable
conditions
exist, or
if
the vital nature
of the
load warrants
it.
Always inspect the breaker after
a
short-circuit
current has
been
interrupted.
At the time of inspection, the following checks should
be
made after the breaker has been deenergized:
1.
Manually operate the breaker several times,
checking
for obstructions or excessive friction. Manual closing of
an
electrically operated breaker may be performed
by the fol-
lowing two
steps:
(1)
Install
maintenance crank (5688386G1) to the motor
gear
reducer
shaft on the front right side of the
breaker.
Ratchetthe
maintenance crank
up
and down untilthe springs
are
fully charged as indicated
by
the distinct click
as
the prop
is set
and prevents any further charging of the
closing
springs. After
the prop
is
set do not apply undue force to the
maintenance handle.
(2)
Depress
the "Spring
Discharge" lever located under
the horizontal support
on the
front frame. The springs should
discharge and
if
the latch is properly reset, the breaker
will
close.
2.
Electrically operate
the
breaker several times
to
check
performance of the electrical
accessories.
3.
Visually check the breaker for
loose hardware on the
breaker
and
the bottom
of
the comoartment for anv hardware
that has fallen from the
breaker.
4.
Remove
the arc quenchers and inspect the
arc
quenchers
and
contacts for breakage or excessive
burning.
5.
The
performance
of the
solid-state
current
trip devices
may be checked with a suitable
test
set. Check
electrome-
chanical devices for positive
trip in accordance with the
in-
structions
in
Maintenance Manual.
6.
Check insulating
parts for evidence
of
overheating
and
for cracks that indicate excessive thermal
aoino.
LUBRICATION
In
general, the circuit breaker requires moderate
lubrica-
tion. Bearing points
and
sliding surfaces should
be
lubricated
at
the regular inspection periods with
a thin film of GE Lubri-
cant D50HD38 (Mobil 28). Before lubricating, remove
any
hardened grease and
dirt from latch and bearing surfaces
with kerosene. ALL EXCESS LUBRICANT SHOULD BE
RE-
MOVED WITH A
CLEAN CLOTFI
TO
AVOID ACCUMULA-
TION OF DIRT OR
DUST.
On
drawout breakers
the contact surface
of
the disconnect
studs should be cleaned and qreased with
GE
Lubricant
D50HD38,
14