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Equipment Description
01.4IB.77020
PowlVac-ND
®
and PowlVac-NDA
™
Series 4
Vacuum Circuit Breakers
This ensures that the control circuits
cannot be disconnected in any position
except the test/disconnected position.
The tripping linkage and roller on
the side of the circuit breaker frame
follows a cam mounted in the circuit
breaker compartment. The cam, in
all intermediate positions between
the test/disconnected and connected
position, depresses the tripping roller.
Depressing the tripping roller actuates
the manual trip operator which holds
the breaker in a trip free condition. The
manual trip operator also actuates the
latch check switch, thus blocking any
electrical closing signal.
The interlock bar attached to the
secondary disconnect also actuates
the secondary trip prop shaft and the
close latch upon removal from the
circuit breaker. This final interlock
ensures that the circuit breaker is in the
open position and the main spring is
discharged prior to removal from the
compartment.
2) Closed Door Racking Mechanism
The closed door racking mechanism
consists of a racking shaft
with
racking crank arms
at each
end, which are supported by the frame side
sheets. The racking shaft also supports
a worm gear assembly
at the
right end just inside the right side sheet.
In addition, the racking crank arms have
rollers attached to each end of the racking
shaft, which engage the vertical slots of
the racking cams in the circuit breaker
compartment. Rotation of the racking
crank arms will drive the circuit breaker
into or out of the connected position. This
action also operates the compartment
shutters.
The two bolts on the left side sheet and the
one bolt on the right side sheet serve as a
positive stop to the crank arm. This positive
stop prevents further rotation of the
racking shaft, thus stopping circuit breaker
travel. At this time, the breaker position
indicator on the front of the circuit breaker
will display “
CONN
”.
Figure 9
Closed Door Racking Mechanism and
Interlock
a. Interlock Cam
b. Worm Gear
c. Racking Shaft
d. Racking Drive Shaft Extension
a
c
b
d