Page 26
The spring release latch can be rotated by two methods:
1.
By
the spring release device
on
power-operated
breakers, as shown
in
Figures 14 and
31
b.
2.
By
the close bar, through the linkage shown
in
Figure
31b.
5.1.6
Circuit
Breaker Tripping
or
Opening Mecha-
nism
Referring to Figure 22c showing the breaker
in
the closed
position, the breaker is tripped open by counterclockwise
rotation
of
the trip shaft. The trip shaft extends across the
left hand part
of
the breaker, from the left hand mecha-
nism side sheet to the left hand breaker side sheet; and
can be rotated by several devices as later described.
Rotation
of
the trip shaft accomplishes breaker opening
as follows: Staying with Figure 22c, the main contacts
(not shown) produce a clockwise twisting force
or
torque
on the pole shaft. This is transmitted
by
the center pole
lever downward through the main drive link to the main
roller. The main drive link at the main roller is connected
to the trip latch by the roller constraining link. The down-
ward force on the main drive link results
in
a pulling force
b} Tripped
1. Trip
Actuator
2. Trip Shaft Lever
3.
Trip Plunger
4. Trip Shaft
5.
Left P.U. Lever
6.
Pole
Shaft
1.8. 33-790-11
on the roller constraining link. This force tends to rotate
the trip latch counterclockwise, but the trip latch is kept
from rotating by overlap
of
the latch surface
of
the trip
shaft. A very small rotation
of
the trip shaft thus releases
the trip latch to rotate counterclockwise to the position
shown
in
Figure 22a. The enlarged views
of
the trip shaft
and trip latch tip
in
Figure 22e show
in
detail the rotation
of
the trip shaft for release
of
the trip latch. Thus the
entire linkage collapses under the force
of
the main con-
tacts and comes to rest with the breaker open, as
in
Fig-
ure 22a. Note that the trip latch is still
in
the released
position, i.e., not reset.
If
the breaker stands open with springs charged as
in
Fig-
ure 22b, and if the trip shaft is held
in
the rotated
or
trip
position,
an
attempt to close will result
in
a trip-free oper-
ation. This is so because, with the trip shaft
in
the trip
position, there is no restraint on the trip latch, so no force
is applied to the main link to close the breaker.
Although certain interlocking operations may
or
will result
in
this trip-free type
of
operation, it causes some extra
shock
on
the mechanism parts. Therefore trip-free opera-
tions should be avoided.
Blcr.Oosed
7.
Actuator
Reset Lever
a) Untripped
c) Actuator Reset
Fig. 24 Actuator
Effective October 1998
Courtesy of NationalSwitchgear.com
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