I.B. 35-240-1
PART III
MAINTENANCE
POLE UN
IT
and with one set of arcing tips just touching,
the clearance between the other two se�s of
Each pole unit (Fig. 3) is mounted on a
arcing contacts should not exceed 1/8 i nch.
separate molded base.
The molded bases are
attached to the aluminum mounting panel and
provide insulation for the breaker studs.
FEELER GAGE
"x"
The upper stud and contact are attached to
the molded base by two bolts.
The moving
contact arm is pivoted on the lower stud and
is attached to the cross bar through insulat
ing links.
The lower stud is fastened to the
molded base by four bolts.
CONTACTS:
(See Figure 3) The DB-75 arcing
contact must touch first on closing and open
last on opening.
Do not adjust one set of contacts without
checking the complete sequence of all poles.
With the breaker open proceed in the following
order:
1.
Turn adjusting n uts (A) on insulating
links to vary main contact pr essure.
Use
. 005 feeler gauge, 1/4 inch wide by 6 inches
long, inserted as shown in Figure 4A to check
clearance.
Feeler
(X)
above contact fingers insures
that they have all been deflected.
Feeler
(Y)
inserted below fingers insures that they
have not gone solid.
2.
Check clearance between cam
(B)
and roller
(C) located between insulating links (D) by
pulling main moving contact arm (E) toward
cross bar with.one hand while using a "push
pull" motion on the moving arc tip (F) with
t he other hand.
If cam is tight against
roller, loosen the elastic nuts
(G) ,
lower
cam and tighten.
If ca.m has more than 1/8
inch clearance to roller, raise cam.
3.
Move stationary arc tips
(H)
to obtain
deflection as shown in Figure 48.
4.
Check the above adjustments on all three
poles.
After all poles have been adjusted
7
64MAX.
FIG. 4A
FIG. 48
WITH
BRE"�E'R
LATCHED
ADJUSTING LIMITS OF MAIN AND ARCING
CONTACTS FOR DB-75 CIRCUIT BREAKERS
I I
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