Westinghouse DBN-1016 Technical Manual page 47

CIRCUIT BREAKER
5. Overcurrent trips failing to re-
set after previous operation.
d. If personnel notes that breaker con-
tacts closed or touched, but that breaker
did not remain closed, then look for:
4
1. Insufficient latch engagement,
incorrect trigger clearance or faulty
latch position. See Figure 1 for de-
tails.
2. Any device which might hold
trip bar in partially tripped position.
3. High inrush currents or faulty
overcurrent trips.
4. Breaker "relay release" trip-
ping relay contacts free too soon.
To check, draw breaker out on rails
and close slowly with manual handle.
The "relay release" (Figure 1-2-5)
should raise relay pin (201) just be-
fore or at same time that breaker
latches closed.
5. Friction preventing PAWL (164)
Figure 1-2-3 from latching under
Pin (177).
6. Premature de-energization of
relay coil due to external interlocks
and relays.
4. There is no set dimension or adjust-
ment of cell interlock trip (Figure 1-2-1).
The gap between lever unit (143) and trip
bar (148) is adjusted between these limits.
a. The gap must be small enough to in-
sure that depressing lever handle (144)
will trip breaker before extension rails
can be lowered.
b. The gap must be large enough to in-
sure that depressing lever handle (144)
until stop pin (145) rest on bottom of hole
in breaker frame will not damage trip bar
(148) by permanently distorting it.
5. The overcurrent trip screw setting is
controlled by screw in trip crank (351)
(Figure 1-2-10).
a. Adjust gap between screw and trip (
finger on breaker until raising of arma-
tures (314), (338) and (330) barely trip
breaker.
b. From this position turn screw (153)
1-1/2 turns in direction to shorten gap.