GEI-86134, Power Circuit Breakers
BREAKER MAINTENANCE
SAFETY PRECAUTIONS
BEFORE INSPECTING OR BEGINNING
ANY MAINTENANCE WORK ON THE
BREAKER, I T MUST BE DISCONNECTED
FROM ALL VOLTAGE SOURCES, BOTH
POWER AND CONTROL, AND BE IN
THE "OPEN" POSITION.
MANUAL HANDLE ADJUSTMENT
On
manually-operated AKR breakers, the closing
springs may be charged either 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-7310A, 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.
6
Fig. 4. AKR-SA-30 breaker
1. Opening spring
2. 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.
v
CONTACT MAINTENANCE
Breakers subjected to frequent interruption of
high currents may eventually require replacement
of their contacts. The general rule for determining
need of replacement is the loss of one-half or more
of the mass of the contact tip 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 amount of force is
developed between the movable and stationary con
tacts when the breaker is closed. This is called
the "wipe" adjustment. "Wipe" is the distance
through which the stationary contacts 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.
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