Arc Chute Removal - GE AKR-30 Series Maintenance Manual

SECTION 8-Contact Maintenance
Breakers subjected to frequent i nterruption of high cur­
rents may eventually req uire replacement of their contacts .
The general rule for determi ning need of replacement is
the loss of one-half or more of the mass of the contact tip
material. Roughening or l ig ht pitting of the contact surface
does not i ndicate loss of ability to carry or i nterrupt current.
When contacts are replaced, they must be adjusted to
ensure that the proper amount of force is developed be­
tween the movable and stationary contacts when the
breaker is closed. This is cal led the "wipe" adj ustment.
"Wipe" is the distance through which the stationary con­
tacts move when the breaker closes. It is measured bet­
ween 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 sl id­
ing or "scrubbing" action to the contacts .
The wipe adjustment infl uences proper arc transfer dur­
ing interruption of fault currents. "Transfer" of the arc is its
forced sequential movement from the intermediate con­
tacts to the arci ng contacts to the arc run ner and finally to
the arc quencher where it is dissipated and exti nguished . It
is recommended that contact wipe be checked periodically
during normal maintenance inspectio ns.
CAUTION:
BEFORE DOING ANY OF THE FOL­
L O WING C O N TA C T A DJ U S TM E N T A N D RE­
P L A CEMENT WO R K,
CONNEC T THE CLOSING SPRING F R O M THE
MECHANISM CAM SHAFT AS DESCRIBED UN­
DER SLO W CLOSING THE BREA KER, SECTION
7.4
MECHANICA L L Y D I S ­
8.1

ARC CHUTE REMOVAL

AND INSPECTION
There are two types of arc chute construction used on
the 800 thru 2000 ampere breakers. They are the cerami c
type shown i n Fig. 5 and the molded type shown i n Fig. 6.
The ceram ic type uses a two piece porcelain frame to
enclose its i nternal parts. The molded type uses a one
piece, glass-fi l led polyester frame.
800
ampere arc c h ute is different from the 1 600 and
The
2000 ampere arc chute, which are identical. Therefore, the
800 ampere arc chute cannot be i nterchanged with the
1 600/2000 ampere arc chute. Also note that a breaker must
have either all ceram ic or all molded type arc ch utes i nstall­
ed, do not i ntermix on the same breaker.
The arc chutes are held in place by retai ners secured by
bolts through the mechanism frame.
uses two retainers and the molded type uses only one.
To remove the arc chutes:
1 . Loosen and back off the retainer bolt locking n ut from
the mechanism frame. They do not have to be removed.
2. Loosen the retainer bolts until the retainer(s) can be
removed.
3. With the retainer(s) removed, lift the arc chutes off for
i nspection.
Inspect each arc chute for excessive burning and erosion
of the arc plates and arc runner. Also look for fractures,
damage to the l i ner material used in the molded arc chute
and damage to the insulation material used in both arc
chutes. Check for any missing parts.
To i nstall the arc chutes:
1 . Replace the arc chutes over each pole u nit.
2. Locate the retainer(s).
3. Tighten the retainer bolts until the arc chutes are
secure. There may be some side to side motion of the arc
chutes, but there m ust not be any front to back motion.
Torque the retai ner bolts to
60
chutes and to 1 00 i n-lbs for the ceramic type. Do not
over tighten.
4. Tighten the locknuts against the mechanism frame
with 1 50 to 1 75 i n-lbs torque.
The ceramic type
30
i n-lbs for the molded type arc
33