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Figure 36: Contact-erosion check
mark dot circled in orange (shown
with circuit breaker open)
42
Fastener check
Inspect all fasteners for tightness. Both
locknuts and retaining rings are used. Replace
any fasteners that appear to have been
frequently removed and replaced.
Manual-spring charging and contact-
erosion checks
Perform the manual-spring charging check
contained on page 12 in the section
"Installation check and initial functional
tests." The key steps of this procedure are
repeated here.
1. Insert the hand-charging crank into the
manual-charge socket at the front of the
operator control-panel. Turn the crank
clockwise (about 48 revolutions) to
charge the closing spring. Continue
cranking until the CHARGED flag appears
in the window of the spring-indicator.
2. Press the close (black) pushbutton. The
contact-position indicator on the
operator-control panel should indicate the
circuit breaker contacts are CLOSED.
3. Perform the contact-erosion check.
Contact erosion occurs when high-fault
currents are interrupted or when the
vacuum interrupter is nearing the limit of
its contact life. Determination of
acceptable contact condition is checked
by the visibility of the white-erosion mark
(refer to Figure 36: Contact-erosion check
mark dot circled in orange (shown with
circuit breaker open)).
The white-erosion mark is located in the
keyway (or slot) on the movable stem of
the vacuum interrupter, near the plastic-
guide bushing.
The contact-erosion check procedure is:
A. Be sure the circuit breaker primary
contacts are CLOSED.
B. Observe the white-erosion mark of
each pole (refer to Figure 32: Trip-
control pushbutton (lower button) on
page 39). When this mark is visible,
contact wear is within acceptable
limits.
4. Press the red trip pushbutton after
completing the contact-erosion check.
Visually verify the DISCHARGED condition
of the closing springs and the circuit
breaker contacts are OPEN.
5. Press the black close pushbutton. Nothing
should happen. The manual-spring check
should demonstrate smooth operation of
the operating mechanism.
Electrical-control checks
The electrical controls of the type GMSG
vacuum circuit breaker should be checked
during inspection to verify absence of any
mechanical damage, and proper operation of
the automatic-spring charging and close and
trip circuits.
Unless otherwise noted, all of these tests are
performed without any control power applied
to the circuit breaker.
High-speed moving parts.
Can result in serious injury.
Tripping spring is charged. If trip latch is moved, the stored-energy
springs will discharge rapidly.
Stay clear of circuit breaker components subject to sudden, high-speed
movement.
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