Vehicle Description
downward displacement of the trip actuator and
elevation of the lever linkage arrangement, which in turn
will lift the interlock levers and elevate the trip-free
pushrod. The elevation of the trip-free pushrod will
actuate trip latch lever and displace the close latch lever,
resulting in the discharge of the closing spring and the
“tripping” (opening) of the circuit breaker prior to
racking.
In short, operating the elevating mechanism handle should
immediately displace the trip-free roller, resulting in the
discharge of the closing spring and the opening of the
circuit breaker, therefore making it impossible to rack a
closed or charged circuit breaker.
Trip-Free In Racking Procedure (Refer to Figure 2)
Figure 2 is a pictorial representation of the circuit breaker
during the racking procedure.
Note that in this position, as well as in any position during
racking the circuit breaker from Disconnect/Test to Connect,
the trip-free roller is displaced counter-clockwise and
“rides” along the face of the cubicle mounted moveable
cam.
Figure 2. Trip-Free/Spring Dump Interlock (Circuit Breaker in Mid-Cycle Racking Position)
As shown in the enlarged view of the circuit breaker
operator, the displacement of the trip-free roller results in
the downward displacement of the trip actuator which in
turn lifts the lever linkage, which results in the elevation
of the interlock levers. The upward displacement of the
interlock levers result in the opening on the normally-
closed motor cutoff switch, preventing the springs from
charging electrically during racking. The elevation of the
interlock levers also lift the trip-free pushrod and trip
pushrod cam, resulting in the displacement of the trip latch
lever and close latch lever, ultimately resulting in the circuit
breaker obtaining a trip-free condition.
The effectiveness of the trip-free interlock can and should
be tested during the racking procedure by following the
steps below:
1. On a de-energized bus, rack the circuit breaker to any
position between Disconnect/Test and Connect. Release
the elevating mechanism handle.
2. Attempt to electrically charge the closing spring. As
the motor cutoff switch (normally closed for operation),
is being held open by the displacement of the trip-free
roller, no spring charging should be observed, therefore,
no electrical close may be initiated.
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