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Equipment Description
01.4IB.77020
PowlVac-ND
®
and PowlVac-NDA
™
Series 4
Vacuum Circuit Breakers
The tripping linkage and roller
beside the breaker frame follow 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.
c. Blocking Interlock
Access to the emergency racking drive
is controlled by a blocking interlock.
The emergency racking access shutter
can only be opened with the circuit
breaker open. Moving the emergency
racking drive shaft shutter downward
prevents the closing of the circuit
breaker by operating a linkage which
blocks the mechanism. If the breaker
is not in the open position, the shutter
cannot be opened enough to insert
the racking handle. This interlock
ensures that the circuit breaker is
open when it is manually racked
into the compartment. Once the
circuit breaker reaches the operating
position and the shutter mechanism is
released, the circuit breaker can now
be closed. When the circuit breaker is
in the closed position, the shutter is no
longer free to move. This blocks the
operation of the emergency racking
drive shaft, deterring any attempt to
remove a closed circuit breaker from the
compartment.
2) Racking Mechanism
The racking mechanism consists of a
racking shaft
with racking
crank arms
at each end which
are supported by the frame side sheets.
The racking motor
is located
at the top of the racking shaft, inside the
circuit breaker frame. 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.
Bolts on the left and right side sheets
provide a positive stop to the left 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”
.