Contact Adjustments; Measurements; Adjusting Center-Pole Contact Wipe And Overlap; Field Discharge Contacts - Center Pole - GE AK-2-50 Maintenance Manual

GEK-7303 Low Voltage Power Circuit Breakers
6 5 4 3 2
1. Springs
2. Insulation
3. Stationary Contact
4. Pin .
5. Screw
6. Movable Contact
7. Pin
8.
Buffer
· 9 •.
Crossbar
10. Adjusting Plate
11.
Bolt
12. Buffer
13. Screw
14. Shims
15. Bolt
16. Pin
17. Pin
13 14
Fig. 17 (227Dl 74) Field discharge c~ntacts (center pole)
When the breaker is tripped, the opening springs
pull crossbar
(9)
downward, opening the breaker's
outer poles. As the crossbar moves downward, link
(A) rotates about a fixed center (17)", collapsing
toggle links (B) and (C) upward, therby closing
center-pole contacts through connecting
link
(D).
Link (C) consists of two
links
riveted together,
forming a single triangular· link.
Contact Adjustments
Measurements
For contact measurements and adjustments
of the two outside poles of the breaker, refer
to POLE UNIT ASSEMBLY.
Contact measurements of the center-pole field
discharge contacts should be made on the left
contact and be
within the
following
limits:
1. Contact wipe, 3/16 in. to 7/16 in.
2. Contact pressure, · 1 0 lb. to 16 lb.
3. Ga_p between contacts when center pole is
open, 1 1/2 in. to 1 3/4 in.
4. Overlap · between the center-pole contacts
and the arcing contacts of the outer poles, 3/16 in ··
to 7/16 in. _ · •
Measurements of the center-pole contact wipe
20
and pressure may be made by following the same
procedure as outlined for the standard pole unit
in POLE UNIT ASSEMBLY: · Overlap of the center-
pole contacts and the outer pole arcing contacts
may be checked by the following procedure:
.
-
.
1. Remove arc quenchers (see ARC QUEN-
CHER). · . .
2. Insert safety pin in push rod. (See Fig. 3
under MAINTENANCE.)
3. Operate closing me~hanism with mainten-
ance handle until arcing contacts of outer poles
just touch.
4. Measure distance between forward edge of
left stationary contact of center pole and surface
of insulation block behind contact.
5.
Continue to operate maintenance closing
handle until center-pole contact opens fully.
6. Repeat measurement described in step 4.
Difference between measurements indicates amount
of overlap.
Adjusting Center-pole Contact Wipe
and Overlap
·{Fig. 17)
If
measurements reveal either incorrect center-
pole contact wipe or incorrect overlap of confacts,
adjustments should be made by the following
procedure: