8.4 CONTACT ADJUSTMENT
AKRT 50/SOH
The contact structure shown in Fig. 48 is used by all
AKRT 50 breaker types. This structure is similar to the AKR
50 structure. There are two movable contact arms, each
acting against single stationary arcing and intermediate
contacts and four stationary mains.
There are two designs used to connect the movable
contact arms to the insulated link. This results in two con
tact adjustment procedures depending on which design
the breaker has.
In the original design the two movable contact arms are
pin-coupled to a metal driving link whose opposite end is
threaded and screws directly into the insulating link. This
arrangement omits the wrench-operated wipe adjustment
stud provided on the AKR-30 and -50 frames. I nstead , wipe
is adjusted by detaching the driving link from the movable
contact arms and then rotating it with respect to the insulat
ing link.
On the AKRT-50 the proper amount of contact wipe
exists if, on a closed breaker, all of the stationary main
contacts have moved away from their stops. This condition
can be checked visually by removing the arc quenchers,
closing the breaker and verifying that all eight stationary
main contacts are "lifted off" their stops. Should wipe ad
justment appear necessary, proceed as follows:
1 . Open the breaker.
2.
Arrange the breaker for slow-closing.
3. Selecting one pole, drift out the coupling pin and
detach the driving link from the movable contact arms.
4. Screw the driving link completely into the insulating
link.
5. Back out the driving link two and one-half turns. Ex
ceed this by whatever amount is necessary to properly
position the link within the movable contact arms.
6. Install the coupling pin and retainer rings.
7.
Using the maintenance hand le, slow-close the
breaker and observe that all eight stationary main contacts
move away from their stops. If this condition is not
achieved, open the breaker, again remove the coupling pin
and back out the driving link an additional half turn .
8. Reassemble, reclose the breaker and recheck wipe.
9. Repeat the above procedure on the other two poles.
In the existing design, the metal driving link uses the
same adjustment as the AKR 50. To perform the wipe
adjustment on this design follow the procedure for the AKR
50, Section 8.3.
FIG. 48 - 2000 AMP CONTACT STRUCTURE
37
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