SECTION 8-Contact Maintenance {Cont.)
8.3
CONTACT ADJUSTMENT -
AKR 50150H & AKRU 50
·
The contact structure shown in Fig. 47 is used by all
AKR50 breaker types. This structure uses two movable
contact arms. Each arm acts against a stationary arcing, a
stationary intermediate and three stationary mains.
The following procedure Is used to perform the wipe ad
justment.
1 . Open the breaker, remove arc quenchers.
2.
Arrange the breaker for slow-closing. The cam roller
must be supported by the
cam
and not the prop. Refer to
Section
5.3.
3.
Select one pole of the breaker and place a thin sheet or
strip of tough insulating material, such as mylar, over the
stationary arcing and intermediate contacts. This strip
should be about two inches wide and must prevent the
arc
ing and intermediate contacts from making contact when
the breaker is closed.
4. Using the ratcheting.maintenance handle, slow-close
the breaker with tl}e insulation held in place. Examine the
insulation to make sure it "over-hangs" below the in
termediate contacts, but not enough to cover the main con
tacts.
5.
Attach a continuity checker (bell-set, light, or ohm
meter) between the upper and lower stud. The checker
should indicate continuity exists.
6.
Facing the breaker, tum the wipe adjustment stud
shown in Fig. 47 clockwise until the checker indicates that
the main contacts are separated.
7. Tum the stud counter-clockwise until the main con
tacts just touch.
a
From this point, advance the stud counter-clockwise
270
degrees. This will be 4-1� flats.
9.
Once the adjustment is complete, verify that the torque
required to just tum the adjustment nut is greater than
40
in-lbs. If less torque is required, carefully add
LOCTITE 220
to the adjustment nut threads. Wipe off any excess
LOC
TITE.
Once the
LOCTITf
is set, recheck the torque valve.
10. Trip the brtrclker, remove the insulating strips.
1 1 . Repeat the above procedure on the other two poles.
FIG. 47 - 1 600 AMP CONTACT STRUCTURE
36
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