GEI-86134,
Power
Circuil Breokers
BREAKER MAINTENANCE
SAFETY PRECAUTIONS
BEFORE INSPECTING
OR BEGINNING
ANY XMINTENANCE WORK
ON THE
BREAKER, I7: MUST BE DISCONNECTED
FROM
ALL VOLTAGE
SOURCES, BOTH
POWER AND CONTROL, AND BE IN
THE
'IOPEN"
POSITION,
MANUAT
HANDTE ADJUST'NENT
On
manually
-
operate d AKR
bre ake rs, the closin
g
springs may be charged
ei.ther by
a
single
135
de-
gree
clockwise handle
stroke
or up
to four
multiple
strokes
of
lesser
swing. The following
adjustment
procedures
should
be
performed
using the single-
stroke method. By
so
doing, proper
multi-stroke
operation
is
assured.
Referring
to Fig.
13
of GEK-?310,
the manual
handle adjustment is
made
via adjustable
link
(16).
The length of
this link is
controlled
by turning
a
double-ended
stud in its center.
A hex
section in
mid-stud can be
engaged by an open-end wrench.
When looking
down
on the breaker, turning the
wrench clockwise
lengthens
the
link.
The opposite
motion
shortens it. The
range
of adjustment
is 300
degrees.
In
the
confined space available,
each
wrench stroke imparts 15 degrees movement.
The
best setting is approximately mid-range.
Fig. 4.
AKR-SA-30
bt,eaher
Opening
spring
Rejection
bracket
If the
link
is too long, the handle
stroke cannot
extend the closing spring
enough
for
it to
go
over
center.
In
this
event, use the maintenance
handle
to complete the
spring charging.
The breaker can
then
be closed and opened
preparatory
to further
shortening of the link.
If the
link
is too short,
one-stroke
charging
is
not
possible.
However, more than
one stroke will
charge the springs.
CONTACT MAINTENANCE
Breakers subjected to frequent
interruption
of
high currents may
eventually require
replacement
of their contacts.
The
generalrule
for
determining
need
of replacenrent
is
the loss
ofone-haLf or more
of
the mass
of the contacttip material. Roughening
or
light
pitting
of
the contact
surface does not
indi-
cate
loss
of ability
to carry
or interrupt
current.
When contacts are replaced,
they
must be ad-
justed
to ensure that the
proper
a:nount
of
force
is
developed
between
the
movable
and
stahonary
con-
tacts
when the
breaker is
closed.
This
is called
the
"wipe"
adjustment.
"Wipe"
is
the distance
throughwhich
the stationarycontacts
move when
the
breaker closes.
It is measured
between
the
point
of
contact
on a stationary
contact when the
breaker
is open,
and
the position
of the same point
when the
breaker
is closed. The
actual wiping motion
is
greater
because
the contacts
over-travel.
"Wiping"
imparts a sliding
or
"scrubbing"
action to the
con-
tacts.
1.
2.
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