Westinghouse DBN-1016 Technical Manual page 13

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the upper stud (lOS), the main contact fingers
(135) and (137), pins (107) and (136), pressure
plate (105), main contact spring (104), arcing
contact (115), the arcing contact spring (113),
pin (Ill) and shunt (112). The main stationary
contact is bolted to the base (101) and the arc-
ing contact is pivoted on pin (111). The main
and arcing contacts are connected electrically
by shunt (112).
. The main stationary contact fingers (135)
and (137) are ball ends which pivot in sockets.
Main contact pressure is equalized by the main
contact spring (104) through pressure plate (105)
and pressure pins (107) and (136).
Limited rotation about pin (111) provides
for arcing contact overtravel while the arcing
contact spring (113) maintains the required con-
tact pressure. The overtravel feature permits
the arcing contact to close first and remain
closed until afte r the main contacts have sep-
arated. 'The contact surfaces of the arcing
contacts are special arc resistant alloy inserts.
The moving contact assembly consists of a
contact arm (123) of copper to which is fastened
arcing contact (120) by two bolts (122) which
are locked by lockclip (121). The main contacts
are an integral part of the moving contact arm
(123) and the contact tips are silver brazed in
position. The auxiliary contacts (129) carry the
current from the moving contact assembly to
the lower stud. Spring (132) provides the re-
quired contact finger pressure between the mov-
ing contact assembly and the lower stud.
1-2-1-4 Arc Chute-(See Figure 1-2-2)
The arc chute (116) mounted above and
surrounding the contact assembly of each pole,
stretches and cools the arc drawn between the
separating contacts so that the arc may be ex-
tinguished and the Circuit opened in the least
possible time. The arc chutes are an extremely
important part of the circuit breaker and a
breaker should never be energized without their
be ing mounte d in place.
Each arc chute consists of a number of
metal plates and asbestos plates (117) supported
in a laminated case and held in place by a
clamping plate, insulating tube spacers (lIS) and
two screws (119) through the insulating spacers
to the molded base (101). When the arc is
drawn by the separating contacts, it moves up
into the chute by magnetic and the rmal action
where it is quickly de-ionized and extinguished.
CHAPTER l-GENERAl INFORMATION
1-2-1-5 Operating Mechanilm-(S .. Figure 1-2-3)
The operating mechanism opens and closes
the circuit breaker by moving the cross bar
(lS7) (Figure 1-2-1) to which the moving con-
tact assemblies are attached. It is mounted
on the top of the shell at the center of the cir-
cuit breaker.
The operating mechanism consists of a
group of toggle links and a latch attached to the
operating mechanism frame on fixed pins (154),
(157), (171), (173), (179) and (lS2). The cross
bar is held by the closing lever (158).
De-
pressing the operating handle moves the oper-
ating mechanism from the open to the closed
position. This is accomplished when the end
of the handle socket (175) forces the first toggle
link (172) upward, pushing the second toggle
link (165), the third toggle link (163) and the
closing lever (15S) ahead of it. The motion of
the toggle linkages is directed by link (160)
which is pivoted at its lower end on pin (155),
in latch (156). Latch (156) in turn is restrained
from moving by roller latch (159) which is
pivoted on pin (179) and engages trigger (ISO)
on the trip lever. The linkage is held in the
closed position by pawl (164).
In electrical operation, plunger rod of the
closing solenoid bears directly on pin (177) thus
engaging linkage and closing breaker.
The mechanism is opened by rotation of
the trip bar (151) counterclockwise. This is
accomplished either by pushing the "Push To
Trip" button, in which case the pushbutton ro-
tates latch (153), or by causing the tripping at-
tachment to strike trip finger (152). In either
case, the counterclockwise rotation of the trip
lever moves trigger (ISO) out of engagement
with the lower end of the roller latch (159),
which in turn permits the roller latch to rotate
counterclockwise out of engagement with latch
(156). Latch (156) is then free to rotate in
response to the pull of the link (160) so that
the mechanism assumes the trip free position
shown in Figure 1-2-3 in which the contacts are
open, but part of the mechanism levers are in
the closed position. In this position pawl (164)
is disengaged permitting the linkage to collapse
to the open position.
Position indicator (170) is an integral part
of the mechanism, formed from sheet metal and
pivoted on pin (l7l). It is visible from the
front of the circuit breaker through a window
in the faceplate and mechanism frame. With
the circuit breaker in the open position shown
1-7