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The spring dump cam profile on the
racking mechanism raises the spring
dump/trip-free interlock upon insertion
of the circuit breaker into the
compartment, or upon withdrawal
from the compartment. The interlock is
raised at about the time the front
wheels pass over the cubicle sill. It
allows the spring dump interlock to be
in the reset (lowest) position at all
other times.
The trip-free cam profile on the racking
mechanism allows the spring dump/
trip-free racking interlock to be in the
lowest position (reset) only when the
circuit breaker is in the TEST or the
CONNECT position. Thus, during
racking, the trip-free/spring dump
interlock is held in an elevated
condition except when the circuit
breaker reaches the TEST or the
CONNECT position. The circuit breaker
can be closed only when the interlock
position is down, and will trip if the
plunger is moved up.
Figure 31: Closed circuit breaker
interlock mechanism in stored-energy
mechanism on page 35 shows the
operating mechanism detail
components which establish a spring
dump condition as the spring dump/
trip-free interlock is actuated by the
spring dump and trip-free cam profiles
on the racking mechanism. The rising
plunger raises a lever attached to the
base of the operating mechanism
enclosure. This lever raises the trip-free
pushrod, which raises the closing
spring release cam. This blocks closing
of the circuit breaker while the circuit
breaker is being racked.
C. Trip-free interlock position -
mechanical interlock
In order to prevent the motor- charging
circuit from "making and breaking" as
the circuit breaker and cubicle
secondary disconnects make or break
physical contact, an electrical switch is
provided.
This switch is mounted in the line of
action taken by the trip-free interlock
plunger that follows the racking-
mechanism cam and is elevated at all
times while the circuit breaker is in the
drawout compartment except when in
the TEST or CONNECT positions.
A striker plate, integral with the trip-free
interlock plunger, engages and operates
(opens) the switch when the plunger is
in an elevated position blocking spring-
charging motor operation. The switch is
closed when the circuit breaker
occupies the TEST or CONNECT position,
allowing the charging motor to operate
automatically.
35
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